CLARK  UNIVERSITY 

'"lebration  Lectures 


">     With  flie  compliments  of  the 
Department  of  Chemistry, 
C-LAKK  UNTFER8IXY, 
Worcester,  -  Mass, 


fr 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 


PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


CHEMICAL  ADDRESSES 

Delivered  at  the  Second  Decennial  Celebration  of 

CLARK  UNIVERSITY, 

ii 

in  September,  1909, 
BY 


Professor  THEODORE  W.  RTCHA.RDS,  of  Harvard  University;  Professor  WIUJAM  A. 
NOYBS,  of  the  University  of  Illinois;  Dr.  WIMJS  R.  WHITNEY,  Director  of  the  Re- 
search laboratory  of  the 'General  Electric  Company;  Professor  JOHN  E.  BUCHER,  of 
Brown  University;  Professor  Juuus  STiEGUTZ,  of  the  University  of  Chicago;  Dr.  P. 
A.  SEVENS,  of  the  Rockefeller  Institute  for  Medical  Research;  Dr.  EDWARD  W. 
WASHBURN,  of  the  University  of  Illinois;  Professor  MARSTON  TAYLOR  BOGERT,  of 
Columbia  University;  Dr.  C.  S.  HUDSON,  of  the  U.  S.  Department  of  Agriculture; 
Professor  ARTHUR  MiCHAKi,,  sometime  Director  of  the  Department  of  Chemistry 
in  Clark  University;  Professor  S.  P.  MULUKEN,  of  the  Massachusetts  Institute  of 
Technology;  Professor  H.  P.  TAiyBOT,  of  the  Massachusetts  Institute  of  Technology; 
Mr.  JESSE  E.  WHITSIT,  of  the  DeWitt  Clinton  High  School,  New  York;  Mr.  MICHAKI, 
D.  SOHON,  of  the  Morris  High  School,  New  York;  and  Dr.  ANDR£  DEBIERNK,  of  the 
University  of  Paris. 


With  a  Preface  by 

M.   A.   ROSANOFF,   Sc.D. 

Professor  of  Chemistry  and   Director  of    the  Chemical   Laboratories   in  Clark 

University 


Published  jointly  by  Clark  University,  Worcester,  Mass.,  and  the  American  Chem- 
ical Society. 


1911. 


.  i. 


I 


PREFACE. 

Clark  University  was  founded  in  1889  as  a  research  university,  an  insti- 
tution in  which  the  best  part  of  the  teaching  and  studying  should  be  car- 
ried on  through  original  investigation.  On  the  one  hand,  and  primarily, 
the  University  was  to  devote  its  activities  to  the  advancement  of  scien- 
tific knowledge.  On  the  other  hand,  it  was  believed  that  genuine 
knowledge  and  habits  of  independent  thought  can  in  no  way  be  acquired 
by  the  mature  university  student  as  surely  as  through  the  labor  of  finding 
new  truth. 

While  the  new  university  has  not  perhaps  attracted  such  attention 
from  the  public  at  large  as  it  would  have  received  had  it  been  attended 
by  large  numbers  of  students,  it  soon  gained  a  high  reputation  among 
men  of  science  both  at  home  and  abroad.  It  has  been  stated  by  good 
authorities  that  the  example  of  Clark  University  has  had  a  profound  in- 
fluence on  the  ideals  and  organization  of  the  American  graduate  schools 
established  since  1889.* 

At  the  time  of  its  foundation  Clark  University  was  almost  unique  in 
this  country  in  its  ideals  and  methods.  Even  at  present  it  can  boast  the 
distinction  of  having  none  but  research  professorships :  chairs  unhampered 
by  the  burdens  of  elementary  teaching  and  routine  administrative  work. 
If  any  member  of  the  University,  professor  or  student,  fails  to  contribute 
his  share  to  the  advancement  of  his  science  and  thus  himself  gain  greater 
and  greater  mastery  over  it,  the  fault  is  not  that  of  the  University's 
organization. 

It  seemed  appropriate  that  the  anniversary  celebration  of  Clark  Uni- 
versity should  consist  in  a  series  of  research  conferences,  and  the  present 
volume  reproduces  most  of  the  chemical  addresses  of  the  Celebration.  In 
organizing  the  conferences,  an  effort  was  made  to  have  all  the  more  im- 
portant chapters  of  American  chemical  research  represented,  and  the  effort 
was  in  large  measure  successful,  owing  to  the  generosity  with  which  a 
majority  of  our  chemical  investigators  responded  to  the  Department's  in- 
vitation. 

The  technical  addresses  have  been  gradually  publisned  in  the  Journal 
of  the  American  Chemical  Society,  the  educational  addresses  in  Science. 

*For  example,  Professor  Stieglitz,  reviewing  the  progress  of  American  chemical 
research,  says:  "The  greatest  recent  impetus  to  all  branches  of  research,  including 
chemistry,  came,  in  my  opinion,  from  the  founding  of  Clark  University,  with  research 
as  its  chief  and  almost  exclusive  field...."  (See  Science,  Vol.  XXVI,  p.  700,  for 
the  year  1907.) 


M3679G3 


The  Chemical  Department  of  the  University  wishes  to  again  express  its 
deep  appreciation  of  the  honor  bestowed  upon  it  by  the  brilliant  lecturers, 
and  its  confidence  that  their  joint  effort  here  will  not  have  been  without 
fruit. 

The  Department,  which  has  recently  been  placed  under  the  director- 
ship of  the  present  writer,  also  wishes  to  assure  the  chemists  of  the 
country  that  it  is  making  a  veritable  effort  to  grow  to  the  ideal  of 
Clark  University,  which  is  the  ideal  of  all  sincerely  scientific  men. 

M.  A.  ROSANOFF. 

November.  1911. 


7 

TABLE  OF  CONTENTS. 

Page.* 
I.  Recent  Investigations  in  Thermochemistry.      By  Professor  Theodore  W. 

Richards X 

II.  Molecular  Rearrangements.     By  Professor  William  A.  Noyes 9 

III.  Organization  of  Industrial  Research.     By  Dr.  Willis  R.  Whitney 16 

IV.  The  Acids  of  the  Phenylpropiolic  Series  and  Their  Condensation  to  Naph- 

thalene Derivatives.     By  Professor  John  E.  Bucher 23 

V.  Catalysis  on  the  Basis  of  Work  with  Imido  Esters.     By  Professor  Julius 

Stieglitz 32 

VI.  On  the  Biochemistry  of  Nucleic  Acids.     By  Dr.  P.  A.  Levene 42 

VII.  The  Fundamental  Law  for  a  General  Theory  of  Solutions.     By  Dr.  Edward 

W.  Washburn 52 

VIII.  A  Review  of  Some  Recent  Investigations  in  the  Quinazoline  Group.     By 

Professor  Marston  Taylor  Bogert 70 

IX.  A  Review  of  Discoveries  on  the  Mutarotation  of  the  Sugars.      By  Dr.  C.  S. 

Hudson 8 1 

X.  Outline  of  a  Theory  of  Organic  Chemistry  Founded  on  the  Law  of  Entropy. 

By  Professor  Arthur  Michael 87 

XI.  Progress  in  Systematic  Qualitative  Organic  Analysis.     By  Professor  S.  P. 

Mulliken 104 

XII.  The  Outlook  for  a  Better  Correlation  of  Secondary  School  and  College  In- 
struction in  Chemistry.      By  Professor  H.  P.  Talbot 113 

XIII.  High  School   Chemistry:    The   Content   of   the   Course.     By  Mr.  Jesse  E. 

Whitsit 125 

XIV.  Chemistry  in  Secondary  Schools.     By  Mr.  Michael  D.  Sohon 130 

XV.  Radioactivity.     By  Dr.  Andre  Debierne 135 

*The  numbers  of  this  column  arc  to  be  found  at  the  bottom  of  pages. 


RECENT  INVESTIGATIONS  IN  THERMOCHEMISTRY.1 

BY  THEODORE  W.  RICHARDS. 
Received  September  17,  1909. 

Within  a  brief  space  of  time,  the  world  has  lost  two  masters  of  thermo- 
chemistry, Marcellin  Berthelot  and  Julius  Thomsen.  To  these  great 
men  chemical  science  owes  much ;  their  places  in  its  history  are  forever  se- 
cure. Each,  by  his  indefatigable  labors,  added  both  new  methods  and 
new  data  to  the  sum  of  human  knowledge;  and  upon  the  broad  founda- 
tion which  they  laid,  all  the  subsequent  development  of  thermochemistry 
must  be  built.  All  honor  to  their  memories!  It  is  no  discredit  to  their 
faithful  work  that  as  science  progresses  many  of  their  methods  must  be 
subjected  to  revision  and  refinement,  for  mankind  approaches  precision  only 
little  by  little,  and  those  workers  who  come  later  have  the  benefit  of  all 
that  has  gone  before,  with  fresh  energy  and  new  years  with  which  to  im- 
prove upon  it.  In  the  same  way,  a  few  decades  hence,  others  will  perhaps 
remodel  the  not  yet  perfect  work  of  the  present  generation,  may  possibly 
marvel  at  inaccuracies  which  have  escaped  our  detection,  and  will  have 
opportunities  for  the  exercise  of  charity  similar  to  those  which  fall  to  our 
own  lot. 

It  is  not  necessary  to  emphasize  the  importance  of  thermochemistry, 
or  to  trace  in  detail  its  history.  You  know  that  the  first  law  of  energy 
was  applied  in  this  science  by  Lavoisier  and  Laplace,  and  by  Hess,  before 
it  was  generalized  by  Mayer,  Joule  and  Helmholtz.  You  are  familiar 
with  the  fact  that  Berthelot  and  Thomsen  and  Stohmann  and  others 
utilized  this  principle  to  determine  the  heats  of  formation  of  most  com- 
mon substances  with  some  degree  of  approximation;  and  that  these  data 
constitute  the  sum  and  substance  of  our  knowledge  of  the  heat  evolved 
during  chemical  reaction. 

Before  we  consider  the  revision  of  these  multifarious  data  which  is  now 
in  progress,  it  is  worth  while  to  pause  for  a  moment  and  think  of  their 
significance. 

Thermochemistry  is  concerned  with  the  total  energy-change  of  a  chemical 
reaction,  and  not  with  the  change  of  the  free  energy,  hence  it  cannot 
serve  as  an  infallible  guide  to  the  tendency  of  a  reaction,  for  preponder- 
ance of  free  energy,  not  of  total  energy,  determines  the  path  which  a  change 
will  take.  Nevertheless,  in  spite  of  this  limitation,  thermochemistry 
includes  some  of  the  most  important  facts  of  the  universe  within  its  scope, 
both  for  the  theorist  and  the  practical  man. 

The  total  heat  given  out  during  any  chemical  change  is  one  of  the  funda- 
mental thermodynamic  data  concerning  that  change.  Its  exact  evalua- 
tion is  necessary  to  the  complete  understanding  of  the  thermodynamics 
of  any  reaction,  and  without  an  understanding  of  the  thermodynamics 
of  a  reaction,  the  phenomena  are  only  half  interpreted.  Although  free 
energy  change  is  that  which  determines  the  tendency  of  the  reaction, 
bound  energy  is  also  significant,  and  the  interpretation  of  bound  energy 
is  being  realized  more  and  more  generally  as  one  of  the  coming  problems 
in  thermodynamics.  But  bound  energy  is  the  difference  between  total 

1  Presented  at  the  Second  Decennial  Celebration  of  Clark  University,  Worcester, 
Mass.,  on  Sept.  16,  1909. 

I 


1276  GENERAL,    PHYSICAL,  AND   INORGANIC. 

energy-change  and  the  free  energy-change,  so  that  all  these  three  quan- 
tities are  as  closely  connected  together  as  is  possible.  In  short,  the  ac- 
curate determination  of  thermochemical  data  is  essential  to  the  precise 
application  of  thermodynamics  to  chemistry. 

To  the  practical  man,  perhaps,  the  matter  takes  on  a  different  aspect — 
although  ultimately  he,  too,  will  profit  more  than  he  can  now  appreciate 
from  the  growth  of  pure  thermodynamics.  He  is  more  immediately 
concerned  with  the  every-day  applications  of  thermochemistry,  espe- 
cially the  developments  of  heat  by  combustion.  Our  text-books  of 
chemistry  discuss  the  union  of  carbon  and  oxygen  with  chief  emphasis 
upon  the  formation  of  carbon  dioxide,  but  that  is  the  least  important 
practical  aspect  of  the  matter.  The  really  essential  thing  is  the  libera- 
tion of  energy,  a  fact  which  falls  within  the  province  of  the  thermochemist. 
Numerous  other  reactions  less  striking  but  no  less  important,  including 
the  maintenance  of  our  own  bodily  heat,  are  concerned  with  the  same 
principles  and  methods.  Hence  it  is  not  too  much  to  say  that  thermo- 
chemistry is  intimately  related  with  every  breath  we  draw.  The  ac- 
curate evaluation  of  its  fundamental  quantities  is,  therefore,  one  of  the 
most  important  fields  of  scientific  advance,  because  accurate  data  are 
needed  to  provide  an  adequate  basis  for  precise  thinking  in  an  inductive 
science. 

Let  us  consider  systematically  the  dimensions  concerned,  in  order  that 
we  may  more  clearly  appreciate  the  advances  which  have  been  made 
possible  in  thermochemical  work  during  the  years  which  have  elapsed 
since  Berthelot  and  Thomsen  carried  out  most  of  their  work.  The  energy 
of  heat  is,  of  course,  calculated  as  the  product  of  two  factors,  temperature 
and  heat  capacity,  and  the  accuracy  of  its  determination  is  directly  pro- 
portional to  the  accuracy  of  measurement  of  each  of  these  dimensions. 

The  advances  in  the  accurate  measurement  of  temperature  during  the 
last  thirty  years  have  been  very  great.  In  the  first  place  the  standard 
of  reference,  namely  the  hydrogen  scale,  has  been  fixed  with  much  greater 
accuracy  than  at  that  early  time.  There  is  very  little  evidence  as  to  what 
the  centigrade  degree,  as  used  by  Thomsen  or  Berthelot,  really  meant. 
In  the  next  place,  the  vagaries  of  the  glass-mercury  thermometer  have 
been  studied  by  Crafts  and  others  with  much  greater  completeness  and 
understanding  than  in  those  earlier  days.  We  know  now  how  uncertain 
its  indications  may  be  when  it  is  not  properly  handled ;  and  we  know,  also, 
how  to  obtain  very  accurate  results  from  this  instrument  when  it  is  prop- 
erly made  and  carefully  used.  Again,  thermometry  has  gained  through 
the  introduction  of  new  fixed  points  between  the  old  classic  ones  of  the 
early  history  of  thermometry;  I  mean  the  transition  temperatures  of 
bi-component  systems.  These  give  a  firm  basis  for  a  thermometric  scale 
in  their  neighborhood  and  thereby  contribute  to  its  certainty  and  defi- 
niteness.  All  these  things  must  be  considered  in  the  thermochemistry 
of  to-day  and  all  contribute  to  an  accuracy  exceeding  that  of  olden  times. 

A  further  gain  has  to  be  found  in  the  introduction  of  the  new  methods 
of  measuring  temperature  electrically,  which,  when  properly  manipulated, 
may  exceed  in  accuracy  the  readings  of  the  mercury  thermometer.  One 
must  not  forget,  however,  that  these  methods  are  subject  to  their  own 
peculiar  and  somewhat  elusive  sources  of  inaccuracy,  and  that  their  use 
does  not  yield  the  unqualified  gain  which  is  sometimes  attributed  to  them. J 
1  Emil  Fischer  and  F.  Wrede  have  made  some  excellent  determinations  in  this  way. 


RECENT  INVESTIGATIONS  IN  THERMOCHEMISTRY.  1277 

Turning  now  to  heat  capacity,  we  find  that  to  some  extent  the  same 
considerations  apply.  Heat  capacity  is,  of  course,  determined  by  com- 
parison with  a  standard  substance,  and  the  comparison  is  made  by  means 
of  some  kind  of  thermometer.  The  sources  of  error  are  partly  eliminated 
here,  however,  because  the  determination  is  a  purely  relative  one  and  does 
not  hark  back  to  the  absolute  standard,  as  in  the  case  of  temperature 
change.  Specific  heats  are  reckoned  by  finding  the  rise  of  temperature 
in  two  approximately  equivalent  masses  of  substance,  one  the  standard 
substance  and  the  other  the  substance  to  be  determined.  If  the  same 
thermometer  is  used  in  each  and  the  quantities  of  substance  are  so  ad- 
justed that  the  temperature  changes  produced  by  a  known  quantity  of 
heat  energy  are  nearly  the  same,  the  inaccuracies  of  the  thermometer 
are  largely  eliminated  when  the  same  thermometer  is  used  as  a  standard 
in  each  set  of  determinations.  Errors  of  reading  the  thermometer  still 
appear,  and  indeed  the  range  of  inaccuracy  here  is  doubled,  because  a 
specific  heat  determination  depends  upon  four  thermometer  readings 
whereas  temperature  change  depends  upon  only  two.  Obviously,  how- 
ever, an  error  in  the  standard  interval  makes  no  difference.  The  degree 
might  really  be  two  degrees  and  its  inaccuracy  would  cancel.  Hence, 
although  the  thermometer  is  used  for  determining  heat  capacity,  the 
uncertainties  of  the  determination  arise  in  part  from  a  different  source 
and  are  chiefly  to  be  traced  to  the  errors  of  calorimetry,  which  deserve 
and  will  receive  detailed  consideration  in  a  few  minutes. 

Before  discussing  the  errors  of  calorimetry  let  us  for  a  moment  discuss 
the  means  of  calculating  the  heat  capacity  of  a  given  system  which  have 
been  used  in  the  determinations  now  accepted  by  the  chemical  world. 
We  find  upon  studying  the  literature  of  the  subject,  that  there  has  been 
considerable  variety  of  usage,  but  that  the  usage  has  rarely,  if  ever, 
been  precise.  Marignac  determined  a  number  of  specific  heats  by  means 
of  a  kind  of  calorifer,  and  Thomsen  also  determined  many  by  means 
of  his  combustion  calorimeter,  but  these  were  seldom  in  either  case  within 
two-tenths  of  one  per  cent.  Therefore  the  values  calculated  from  them 
could  not  be  expected  to  be  closer  than  this,  if  as  close,  to  the  truth. 
Work  of  others  has  not  yet  actually  been  used.  Berthelot  relied  largely 
on  Marignac' s  determinations  or  more  commonly  adopted  very  rough 
approximations  by  assuming  that  the  heat  capacity  of  the  solution  is 
equal  to  that  of  a  like  volume  of  water — in  other  words,  that  the  specific 
heat  of  a  solution  is  inversely  proportional  to  its  specific  gravity.  This 
method  of  calculating  may  easily  yield  results  several  per  cent,  aside 
from  the  truth  with  concentrated  solutions. 

Moreover,  we  find  a  general  haziness  concerning  the  question  as  to 
whether  the  heat  capacity  of  the  factors  or  of  the  product  of  reaction  is 
to  be  used  in  the  calculation.  Should  one  multiply  the  temperature 
rise  by  the  heat  capacity  of  the  factors  in  order  to  obtain  the  heat  evolved, 
or  is  it  the  products  which  must  be  considered  as  having  been  raised 
through  the  range  of  temperature  in  question?  Only  very  recently  has 
this  question  been  answered  scientifically,  and  its  answer  is  simply  this: 
either  the  one  or  the  other  may  be  used,  provided  that  it  is  used  intelli- 
gently. When  the  heat  capacity  of  the  factors  is  used  in  calculating 
the  result,  this  result  corresponds  to  the  heat  evolved  by  the  reaction 
occurring  isothermally  at  the  final  temperature  attained  when  the  adiabatic 
change  is  completed,  whatever  that  may  be.  On  the  other  hand,  when  the 


1278  GENERAL,    PHYSICAL  AND   INORGANIC. 

heat  capacity  of  the  products  is  used,  the  result  corresponds  to  the  heat  of 
isothermal  reaction  at  the  initial  temperature.  When  there  is  no  change 
of  heat  capacity  during  the  reaction,  the  results  of  the  two  methods 
will,  of  course,  be  identical.  In  other  words,  in  this  last  case  the  heat 
evolved  will  be  independent  of  the  temperature  at  which  the  reaction 
takes  place,  according  to  the  well-known  thermodynamic  rule  of  Kirch- 
hoff.1 

Further  uncertainty  concerning  heat  capacity  arises  from  the  fact  that 
the  specific  heat  of  the  standard  substance,  water,  changes  with  the 
temperature  and  that  therefore  no  expression  for  heat  capacity  is  definitely 
fixed  without  a  qualifying  phrase.  In  order  to  overcome  this  disadvan- 
tage a  proposition  of  Ostwald's  to  use  the  absolute  C.  G.  S.  scale  has  been 
revived  and  a  convenient  standard  of  heat  capacity,  namely  the  capacity 
raised  one  centigrade  degree  by  one  joule  of  energy,  has  been  chosen. 
This  unit  fixes  the  dimension  of  heat  capacity  much  more  definitely  than 
the  old  uncertain  and  changing  one.  Out  of  respect  to  the  memory  of 
one  of  the  founders  of  the  first  law  of  energy,  the  name  "mayer"  has  been 
suggested  for  this  unit  and  its  introduction  seems  to  afford  help  in  teach- 
ing as  well  as  to  add  precision  to  scientific  statement.2 

In  the  coming  revision  of  thermochemical  data  all  the  early  incomplete- 
nesses in  these  respects  will  be  eradicated,  and  the  matter  will  be  put 
upon  the  best  basis  possible  to-day. 

What  now  are  the  chief  errors  of  calorimetry,  which  affect  both  the 
determination  of  specific  heat  and  of  reaction  heat? 

Any  one  with  any  calorimetric  experience  whatsoever  will  recognize 
that  the  greatest  cause  of  uncertainty  in  results  of  this  kind  is  the  cooling 
effect  of  the  surroundings  of  the  calorimeter.  The  errors  of  thermometric 
reading,  of  the  lag  of  the  thermometer  behind  the  temperature  of  the 
surrounding  medium,  and  all  other  uncertainties  are  trifling  compared 
with  this.  Therefore  precise  calorimetry  is  largely  a  question  of  properly 
correcting  for  this  cause  of  uncertainty,  or  else  avoiding  it  altogether. 
The  well-known  methods  of  Rumford  and  of  Regnault  as  amplified  by 
Pfaundler,  serve  to  a  certain  extent  to  correct  for  the  effect  of  the  ex- 
change of  heat  with  the  environment.  But  the  former,  although  it  has 
been  much  used  in  thermochemical  work,  is  greatly  at  fault; and  the  latter, 
although  far  better,  is  still  imperfect.  Rumford  started  his  determination 
as  much  below  the  temperature  of  the  air  around  as  he  finished  above 
this  temperature,  supposing  that  the  intake  of  heat  during  the  first  part 
of  the  operation  would  balance  the  outgo  during  the  latter  part.  We 
have  been  able  to  show  that  this  is  by  no  means  the  case — at  any  rate 
in  a  vessel  containing  a  solution  and  enclosed  in  a  jacket  of  definite  tem- 
perature. Hence  Rumford's  method  is  not  a  very  close  approximation. 
The  Regnault-Pfaundler  method  depends  upon  Newton's  law  of  cooling, 
which  under  certain  circumstances  has  been  shown  to  be  fairly  accurate. 
We  must  remember,  however,  that  the  cooling  of  the  vessel  is  due  to 
convection  and  conduction  as  well  as  to  radiation,  so  that  the  exact 
fulfilment  of  Newton's  law  is  hardly  to  be  expected.  Moreover  the 
evaluation  of  the  rate  of  cooling  depends  upon  the  taking  of  a  number 
of  thermometric  readings  which  are  "caught  on  the  wing,"  as  it  were, 
while  the  thermometer  is  moving.  Hence,  although  the  Regnault- 

1  Richards,  THIS  JOURNAL,  25,  209  (1903). 
1  Proc.  Amer.  Acad.,  36,  327  (1901). 


RECENT  INVESTIGATIONS  IN  THERMOCHEMISTRY.  1279 

Pfaundler  method  may  serve  with  sufficient  approximation  for  quick 
reactions,  it  still  leaves  much  uncertainty  in  reactions  which  extend  over 
many  minutes ;  and  even  in  quick  reactions  the  lag  of  the  cooling  correction 
may  introduce  some  error.  Further,  many  fundamental  processes  are 
slow;  and  among  them  must  be  catalogued  the  determination  of  specific 
heat,  or  heat  capacity,  because  considerable  time  is  needed  as  a  rule  to 
communicate  the  heat  to  the  substance  to  be  studied. 

It  was  with  a  view  to  eliminating  these  disadvantages  that  there  has 
recently  been  put  into  practice  at  Harvard  a  method  of  calorimetry 
which  wholly  eliminates  the  correction  for  cooling  by  causing  the  tem- 
perature of  the  environment  around  the  calorimeter  to  change  at  the 
same  rate  as  the  calorimeter  itself.  It  is  surprising  that  this  obvious 
and  easily  carried  out  device  had  not  been  applied  before.  It  had,  indeed, 
been  suggested  by  S.  W.  Holman1  in  1895,  although  this  paper  was  un- 
known to  me  at  the  time  of  the  first  Harvard  work.  The  somewhat 
similar  device  used  in  the  respiration  calorimeter  of  Atwater  and  Benedict, 
suggested  perhaps  even  before  this,  is  not  exactly  comparable.  In  the 
respiration  calorimeter  the  environment  is  not  essentially  changed  in 
temperature.  It  is  merely  kept  constant,  as  is  also  that  of  the  calorim- 
eter, by  a  suitable  quantitative  cooling  device.  Hence,  so  far  as  I  am 
aware,  the  Harvard  device  was  the  first  one  in  which  the  surroundings 
of  the  calorimeter  were  changed  in  temperature  by  any  considerable 
amount  during  the  progress  of  the  experiment. 

If  the  surrounding  jacket  about  a  calorimeter  is  thus  changed  in  tem- 
perature at  exactly  the  same  rate  as  the  temperature  of  the  calorimeter 
itself,  it  is  obvious  that  the  calorimeter  will  neither  gain  nor  lose  heat 
from  its  equally  hot  surroundings,  excepting  for  the  negligible  quantity 
of  heat  required  to  warm  the  small  quantity  of  air  immediately  in  contact 
with  it  inside  the  jacket.  Thus  a  calorimetric  reaction  may  be  made 
really  adiabatic. 

Obviously  there  are  several  ways  in  which  the  outside  water  jacket  in 
a  calorimeter  might  be  heated  in  order  to  accomplish  this  purpose.  The 
simple  device  of  pouring  in  hot  water  might  be  employed,  or  the  water 
might  be  warmed  by  an  electrically  heated  resistance  coil,  or  the  jacket 
itself  might  be  made  the  scene  of  a  chemical  reaction  of  the  same  speed 
and  thermal  intensity  as  that  within  the  calorimeter  itself. 

Of  these  and  other  methods  which  suggested  themselves  the  last  named 
seemed  the  most  convenient  and  suitable  for  a  chemical  laboratory. 
It  has  the  special  advantages  that  before  the  beginning  of  operations 
all  the  apparatus  and  material  employed  may  be  at  the  temperature  of 
the  room;  that  the  maximum  temperature  attained  may  be  easily  cal- 
culated with  great  nicety;  that  no  point  in  the  system  can  ever  exceed 
this  maximum  temperature,  if  the  reaction  is  suitably  chosen;  and  that 
the  speed  of  the  reaction  may  be  simply  regulated  by  a  stop  cock  ad- 
mitting one  of  the  reacting  substances.  A  reaction  easily  regulated 
and  well  suited  to  this  purpose,  namely,  the  neutralization  of  an  alkali 
with  an  acid,  was  chosen  for  this  purpose. 

The  form  of  apparatus  originally  devised  consisted  of  a  lower  jacket 

containing  alkali  and  a  separate   movable   lid.     More  recently  we  have 

found  it  convenient  to  enclose  the  calorimeter  wholly  in  a  water-tight 

vessel — a  sort  of  submarine,  provided  with  suitable  conning  towers  or 

1  Proc.  Am.  Acad.,  31,  252  (1895). 


1280  GENERAL,   PHYSICAL  AND  INORGANIC. 

periscopes.1  This  water-tight  compartment  is  wholly  immersed  in  the 
alkali  to  which  is  added,  little  by  little,  sulphuric  acid  in  order  to  keep 
the  bath  precisely  at  the  same  temperature  as  the  interior,  however 
much  this  may  be  changed.  Violent  agitation  of  the  warming  alkali 
is  necessary  in  order  that  the  heat  may  be  quickly  distributed  throughout 
the  whole  mass,  and  the  interior  of  the  calorimeter  must  be  agitated  also 
more  energetically  than  has  usually  been  the  custom,  if  great  precision  is 
needed.  In  passing,  I  may  state  that  we  have  evidence  showing  that 
in  the  past  no  one  has  stirred  his  calorimeter  violently  enough.  The 
burettes  delivering  the  sulphuric  acid  into  the  alkaline  environment 
are  graduated  in  tenths  of  degrees,  instead  of  in  cubic  centimeters,  so 
that  a  small  deficiency  in  temperature  may  be  instantly  corrected  with  a 
minimum  of  mental  arithmetic. 

This  form  of  chemical  calorimeter  serves  not  only  to  determine  with  great 
accuracy  specific  heats,  but  also  to  estimate  the  thermal  output  of  all 
forms  of  chemical  reactions.  With  it  series  of  determinations  of  many 
kinds  are  in  progress. 

In  the  first  place  let  me  describe  somewhat  more  closely  the  determina- 
tion of  specific  heat  with  this  apparatus,  because  upon  this  determination 
the  calculation  of  all  other  thermochemical  results  must  depend.  Within 
the  platinum  calorimeter,  enclosed  in  its  submarine,  is  immersed  a  small 
platinum  bottle;  and  inside  of  this  bottle  a  carefully  measured  chemical 
reaction  is  allowed  to  take  place  which  communicates  its  heat  to  the 
calorimeter.  By  placing  in  the  calorimeter,  in  the  first  place  water, 
and  in  the  next  place  the  unknown  liquid  whose  specific  heat  is  to  be 
determined,  and  each  time  allowing  the  measured  reaction  to  occur 
within  the  innermost  platinum  bottle,  a  direct  comparison  of  the  specific 
heats  of  the  standard  and  the  unknown  liquid  is  obtained.  As  the  results 
agree  within  one-twentieth  of  one  per  cent.,  the  average  of  many  experi- 
ments must  be  much  nearer  than  this,  and  it  is  not  unreasonable  to  be- 
lieve that  the  results  thus  obtained  are  at  least  five  times  as  accurate  as 
those  of  Thomson  or  Marignac. 

Having  used  this  device  and  method  for  determining  the  specific  heats 
of  liquids,  it  is  now  possible  to  proceed  with  the  more  accurate  evaluation 
of  reactions  in  which  liquids  take  part.  In  two  recent  investigations 
the  heats  of  neutralization  of  the  acids  and  alkalis  on  the  one  hand  and 
the  heats  of  solution  of  metals  in  acids  on  the  other  hand  have  been  studied. 
Time  does  not  permit  the  detailed  statement  of  the  various  precautions 
necessary  in  these  determinations.  The  former  problem  is  of  special 
interest  because  of  its  relation  to  the  theory  of  electrolytic  dissociation, 
and  our  revision  of  this  work  was  prompted  by  the  desire  to  discover  the 
extent  of  the  deviation  of  the  several  results  for  strong  acids  from  the 
constant  value,  137  calories  or  57  kilo  joules.  Several  unexpected  points 
were  brought  out  in  the  investigation,  the  most  important  being  the 
irregularities  in  the  results  produced  by  the  unequal  distribution  in  heat 
during  mixing  and  also  the  grave  errors  caused  in  previous  results  by  the 
presence  of  carbonate  in  the  alkali.  The  investigation  is  not  yet  finished, 
but  has  already  shown  that  many  of  the  accepted  results  are  much  in 
error  even  for  this  simple  process  of  neutralizing  an  acid  by  an  alkali. 

The  heats  of  solution  of  metals  in  acids  are  among  the  most  essential 

1  A  device  of  this  kind  was  employed  by  Richards  and  Forbes,  Publications  of  the 
Carnegie  Inst.,  56,  52  (1906). 


RECENT  INVESTIGATIONS  IN  THERMOCHEMISTRY.  1 28 1 

and  fundamental  of  thermochemical  data.  The  heats  of  formation  of 
all  the  metallic  compounds  depend  upon  them,  because  through  them 
the  heat  values  are  referred  back  to  the  element.  Hence  it  is  highly 
important  for  exactness  in  thermochemistry  that  these  values  be  deter- 
mined vrith  great  precision. 

As  a  matter  of  fact,  in  the  past  certain  difficulties  have  interfered  with 
the  perfection  of  the  measurements.  First  and  foremost  among  these 
is  the  fact  that  the  heat  of  solution  of  a  metal  requires  much  time,  and 
therefore  the  always  somewhat  uncertain  correction  for  cooling  in  the 
usual  method  becomes  a  serious  fraction  of  the  whole  rise  of  temperature. 
In  the  second  place,  the  method  generally  used — namely,  the  plunging 
of  a  weigied  sheet  of  metal  into  acid,  and  then  withdrawing  it,  checking 
the  reactbn  as  soon  as  possible,  and  determining  the  amount  dissolved 
by  loss  k  weight — is  open  to  serious  criticism.  It  is  impossible  that 
the  withdrawal  should  be  so  quick  as  to  introduce  no  error  in  the  result. 

The  new  method  of  adiabatic  calorimetry,  recently  used  at  Harvard, 
seems  to  b;  especially  suitable  for  such  cases  as  this.  With  it  cadmium, 
zinc,  magresium,  aluminium  and  iron  have  already  been  investigated, 
and  very  concordant  and  satisfactory  results  have  been  obtained.  Here 
again  much  greater  purity  of  material  than  has  been  usual  in  work  of 
this  sort  wa;  sought,  and  the  results  justify  the  trouble  thus  taken.  There 
can  be  no  dcubt  that  in  these  cases  also  the  older  work  was  defective. 

The  heats  of  combustion  of  organic  substances  form  another  very  im- 
portant fiek  for  thermochemical  research.  These  reactions  carried 
out  in  the  cdorimetric  bomb  of  Berthelot  seemed  especially  suitable  for 
the  application  of  the  new  method  of  calorimetry,  and  formed  indeed 
one  of  the  first  series  of  experiments  to  which  it  was  applied.  The  com- 
bustion of  sold  substances  such  as  sugar  presents  no  difficulty  and  imagi- 
nation can  easily  picture  the  way  in  which  this  process  might  be  carried 
out  in  an  aciabatic  calorimeter.  Several  long  series  of  experiments 
with  typical  sibstances  of  this  sort  have  been  made  in  order  to  test  the 
method,  with  satisfactory  results. *  The  combustion  of  liquids  is  a  more 
difficult  probhm.  As  you  well  know,  Thomsen  endeavored  to  burn 
liquids  by  firs;  vaporizing  them  with  the  help  of  electrically  generated 
heat  in  his  socalled  "universal  burner."  We  now  know  that  some  of 
the  superfluous  heat  from  the  electric  coil  must  have  found  its  way  into 
the  calorimete",  so  that  these  results  are  usually  too  high.  Berthelot 
and  Stohmann  on  the  other  hand,  determined  the  heat  of  combustion 
of  organic  liquids  by  saturating  cellulose  with  the  liquid,  which  was  then 
ignited  in  the  lomb.  This  latter  method  of  procedure  is  evidently  open 
to  the  error  catsed  by  a  varying  loss  of  the  organic  liquid  by  evaporation. 
Not  all  the  vaoor  of  the  organic  liquid  spread  throughout  the  bomb  is 
capable  of  beirg  burnt,  hence  Berthelot's  results  for  volatile  liquids  are 
probably  all  t>o  low.  The  truth  would  be  expected  to  lie  somewhere 
between  them  Thomsen's  results  for  the  more  volatile  liquids  being  prob- 
ably the  more  accurate  because  there  the  accidental  heating  from  his 
apparatus  was  unimportant,  and  Berthelot's  results  for  the  less  volatile 
liquids  being  better  because  there  the  loss  through  evaporation  would 
cause  less  error. 

We  sought  to  overcome  these  difficulties  by  enclosing  the  organic  liquid 
in  a  small,  /ery  thin  glass  bulb,  flattened  on  the  sides  and  completely 

1  Proc.  Aner.  Acad.,  42,  573  (1907). 


1282  GENERAL,    PHYSICAL   AND   INORGANIC. 

full  of  liquid.  No  difficulty  is  found  in  making  such  bulbs,  and  they 
will  stand  several  hundred  atmospheres  of  pressure  without  bursting, 
if  completely  full  of  liquid,  because  the  glass  of  the  flattened  sides  is  suffi- 
ciently flexible  to  permit  of  considerable  compression.  These  closed  glass 
bulbs  were  put  inside  the  bomb  in  a  very  small  platinum  crucible,  and 
upon  a  thin  glass  shelf  above  them  was  placed  a  small  weighed  quantity 
of  powdered  sugar.  The  sugar  was  ignited  first  in  the  usual  way.  This 
exploded  the  bulb  and  instantly  lighted  the  vapor  of  the  liquid  at  all 
points  so  that  none  escaped  combustion.  In  this  way  we  have  been  able 
to  show  that  the  heat  of  combustion  of  volatile  organic  liquids  is  as  a 
rule  distinctly  higher  than  Stohmann  and  Berthelot  supposed  ft  to  be. 
We  have  unquestionable  evidence  that  complete  combustion  of  their 
vapor  has  at  last  been  attained.  These  methods  open  the  way  to  an  un- 
limited amount  of  further  experimentation,  and  promise  to  afford  results 
upon  which  interesting  theoretical  considerations  may  be  founded. 

It  is  a  pleasure  to  acknowledge  my  thanks  to  my  several  assistants,  Pro- 
fessor A.  B.  Lamb,  and  Drs.  L.  J.  Henderson,  G.  S.  Forbes,  H.  I/.  Frevert, 
A.  W.  Rowe,  R.  H.  Jesse,  Jr.,  and  L.  L.  Burgess  for  their  expert  assistance 
in  these  protracted  and  often  tiresome  researches,  as  well  as  to  express  my 
obligations  to  the  Cyrus  M.  Warren  Fund  of  Harvard  University,  the 
Rumford  Fund  of  the  American  Academy  of  Arts  and  Science  and  espe- 
cially to  the  Carnegie  Institution  of  Washington,  for  generois  pecuniary 
help  in  the  prosecution  of  the  work. 

Before  closing  let  me  review  briefly  the  recent  advance!  in  thermo- 
chemistry which  I  have  attempted  to  enumerate.  In  the  first  place, 
the  thermometric  scale  has  been  far  more  definitely  fixed  than  it  was 
thirty  years  ago.  In  the  next  place,  the  determination  of  specific  heat 
and  therefore  of  heat  capacity  has  been  put  upon  a  scienlffic  basis  and 
its  precise  treatment  in  the  calculation  of  thermochemical  results  has  been 
pointed  out.  In  the  next  place  the  most  serious  correction  tor  all  thermo- 
chemical results  in  the  past,  namely  the  cooling  correction  has  been  en- 
tirely obviated  by  the  use  of  the  method  preventing  loss  of  my  heat  from 
the  calorimeter  by  enclosing  the  latter  in  a  jacket  of  similarly  changing 
temperature.  Again  the  necessity  for  more  active  agitatim  of  the  con- 
tents of  the  calorimeter  has  been  demonstrated,  and  the  necessity  of  the 
use  of  very  pure  materials  has  been  put  beyond  question.  In  every  case 
the  effort  has  been  made  to  insure  the  completeness  of  tte  reaction  and 
to  correct  for  any  side  reactions  which  may  take  place  at  the  same  time, 
so  that  the  final  results  may  represent  truly  the  data  sought.  In  short 
the  effort  has  been  made  to  apply  to  these  fundamental  figtres  concerning 
chemical  energetics  the  same  kind  of  precision  which  has  recently  been 
attempted  in  the  revision  of  atomic  weights;  and  although  on  account 
of  the  greater  complexity  of  the  problem  the  percentage  accuracy  thus 
far  reached  has  probably  not  equaled  that  in  the  case  of  atomic  weights, 
one  cannot  help  thinking  that  the  proportional  gain  ovei  the  previous 
investigations  is  perhaps  as  great  in  this  case  as  in  the  other. 

HARVARD  UNIVERSITY,  CAMBRIDGE,  MASS. 


MOLECULAR  REARRANGEMENTS.1 

BY  WILLIAM  A.  NOYES. 
Received  September  16,  1909. 

"The  end  of  chemistry  is  its  theory.  The  guide  in  chemical  research 
is  a  theory"  (Phil.  Mag.  [4],  16,  104  (1858)).  With  these  words  A.  S. 
Couper  began  one  of  the  most  remarkable  papers  in  the  history  of  chem- 
istry. At  the  time  when  he  wrote  the  system  of  types  advocated  by 
Gerhardt  had  come  into  very  general  favor.  Chemists  were  busy  arrang- 
ing the  compounds  of  carbon  and  of  other  elements  as  well,  in  classes 
according  to  a  few  simple  types,  especially  in  accordance  with  the  type 
of  water  and  its  multiples.  The  advantages  of  the  system  in  comparison 
with  what  had  gone  before  were  very  evident  and  organic  chemistry 
was  making  rapid  progress  with  its  aid.  It  answered  very  well  for  the 
classification  of  many  of  the  compounds  then  known  and  as  a  guide  in 
the  discovery  of  a  great  many  new  ones.  And  most  of  the  chemists  of 
that  day,  as  always,  were  satisfied  in  working  away  at  the  discovery  of  a 
vast  array  of  new  facts  and  marshaling  these  in  accordance  with  a  highly 
mechanical  theory  with  very  little  thought  about  its  philosophical  basis. 

Under  these  conditions  two  master  spirits,  Couper  and  Kekul£,  suc- 
ceeded, entirely  independently,  in  grasping  those  simple  principles  which 
lie  at  the  foundation  of  our  knowledge  of  the  structure  of  compounds 
of  carbon.  Only  as  the  result  of  an  unfortunate  accident  was  Kekul£'s 
paper  published  before  that  of  Couper. 

It  is  interesting,  and  I  think  profitable,  for  us  to  recall  that  it  was 
chiefly  a  consideration  of  the  philosophical  basis  for  Gerhardt's  system 
which  led  Couper  to  reject  it  and  propose  something  better.  In  criticizing 
the  system  he  says  of  Gerhardt  "He  is  led,  not  to  explain  bodies  according 
to  their  composition  and  inherent  properties,  but  to  think  it  necessary 
to  restrict  chemical  science  to  the  arrangement  of  bodies  according  to 
their  decomposition,  and  to  deny  the  possibility  of  our  comprehending  their 
molecular  constitution.  Can  such  a  view  tend  to  the  advancement  of 
science?  Would  it  not  be  only  rational,  in  accepting  this  veto  to  renounce 
chemical  research  altogether?" 

I  have  dwelt  thus  on  Couper's  point  of  view  because  it  carries  with 
it,  as  it  seems  to  me,  a  lesson  which  we  chemists  of  to-day  may  well  take 
to  heart.  Very  few  are  gifted  with  the  insight  of  a  Dalton,  a  Faraday, 
a  Couper  or  a  Rutherford  but  when  a  glimpse  of  the  real  things  which 
lie  beneath  the  phenomena  which  we  observe  comes  to  such  an  one  it 
may,  guide  the  development  of  science  for  a  decade,  for  a  century,  or 
even,  if  sufficiently  true,  for  all  time.  And  it  seems  possible  that  if  we 
directed  our  thoughts  more  toward  fundamental  problems  instead  of 
towards  the  accumulation  of  compounds  and  of  facts  which  are  little 
more  than  permutations  of  compounds  and  facts  already  known,  more 
real  progress  could  be  made. 

The  new  principles  proposed  by  Couper  were  very  simple:  First,  that 
atoms  show  "degrees  of  affinity"  or  as  we  should  call  it,  valence,  and 
second,  that  carbon  atoms  can  combine  with  each  other.  But  these  two 
simple  principles  have  been  the  foundation  on  which  chemists  have  built 
a  knowledge  of  the  structure  of  one  hundred  thousand  compounds  of 
1  An  address  delivered  at  Worcester,  Mass.,  September  14,  1909,  at  the  celebra- 
tion of  the  twentieth  anniversary  of  Clark  University. 


1369  MOLECULAR  REARRANGEMENTS. 

carbon.  These  principles  involve  a  knowledge  of  the  actual  arrangement 
of  atoms  within  the  molecule  in  the  sense  of  the  order  of  their  successive 
attachments  to  each  other.  Thus  far,  at  least,  they  are  accepted  by  all 
active  workers  in  organic  chemistry  and  there  is,  among  these,  a  prac- 
tically universal  belief  that  atoms  and  molecules  actually  exist  and  that 
there  is  something  in  the  structure  of  the  molecules  which  actually  cor- 
responds to  our  formulas.  The  two  principles  just  stated  have  been 
further  extended,  especially  by  the  study  of  optically  active  and  of  cyclic 
compounds  to  include  still  more  definite  ideas  with  regard  to  the  actual 
arrangement  of  atoms  in  space  and  this  development  of  stereochemistry 
has  also  received  very  general,  though  not  quite  universal,  acceptance. 

For  a  clearer  understanding  of  molecular  rearrangements  we  are  in 
need  of  more  definite  knowledge  with  regard  to  the  nature  of  those  in- 
teratomic forces  or  attractions  which  hold  atoms  together  in  molecules 
and  which  also  cause  atoms  of  different  molecules  to  react  with  each 
other.  Many  theories  with  regard  to  these  forces  have  been  proposed 
but  none  has,  as  yet,  received  any  very  general  acceptance  and  the  majority 
of  chemists  feel  that  any  satisfactory  knowledge  of  this  sort  is  beyond 
our  reach.  But  in  1858  nearly  all  chemists  believed  that  any  definite 
knowledge  of  the  arrangement  of  atoms  in  chemical  compounds  was 
impossible,  yet  all  of  the  facts  for  the  acquirement  of  such  knowledge 
were  already  in  their  hands  and  it  only  needed  a  clear  statement  of  the 
simple  principles  proposed  by  Couper  and  by  Kekule"  and  the  application 
of  those  principles  in  the  explanation  of  facts  already  known  to  make 
clear  the  structure  of  a  large  number  of  substances.  Is  it  not  possible 
that  the  answer  to  other,  equally  fundamental  questions  lies  at  our  hands 
to-day? 

It  is  in  the  hope  that  this  may  be  so  that  I  shall  venture  to  state  some 
of  these  fundamental  questions  as  they  present  themselves  to  me. 

The  first  of  these  is  as  to  the  nature  of  the  attractive  forces  between 
atoms.  The  question  is,  perhaps,  bound  up  with  that  of  the  nature  of 
attraction  between  material  bodies  in  general  and  may  be  equally  far  from 
a  solution.  Newton  seems  to  have  assumed  an  attractive  force  as  an 
inherent  property  of  matter  and  most  of  the  discussion  of  atomic  forces 
starts  with  a  similar  tacit  assumption.  But,  as  soon  as  the  question  is 
raised  the  mind  revolts  against  the  assumption  of  a  force  exerted  through 
space  without  a  medium.  Physics  has  abandoned  any  idea  of  inherent 
attractive  or  repulsive  forces  in  sound,  light,  heat  or  electricity  and  has 
accepted  a  kinetic  explanation  instead.  Is  it  not  probable  that  we  must 
ultimately  do  the  same  for  atomic  forces?  The  discoveries  in  connection 
with  radium  have  made  us  familiar  with  the  notion  that  the  atoms  are 
very  complex  in  their  structure  and  that  their  parts  may  possess  an  almost 
inconceivable  amount  of  kinetic  energy.  The  spectroscope  long  ago 
demonstrated  to  us  that  such  an  atom  as  that  of  iron  can  send  out  im- 
pulses through  the  ether  similar  in  complexity  to  those  impulses  of  sound 
which  come  from  a  whole  orchestra.  It  seems  altogether  probable  that 
these  impulses  come  from  motions  within  the  atom  and  not  from  vibra- 
tions of  the  atom  as  a  whole.  If  we  think  of  such  intraatomic  motions 
as  general  and  that  such  motions  within  the  atoms  may  produce  effects 
which  are  transmitted  through  the  ether,  a  kinetic  explanation  of  atomic 
and  molecular  attraction  seems  possible. 

The  second  question  with  regard  to  the  atomic  forces  is  whether  these 

10 


ORGANIC  AND   BIOLOGICAL.  1370 

forces  are  purely  attractive,  resembling  gravitation,  or  polar,  partly 
attractive  and  partly  repulsive,  resembling  or  identical  with  electrical 
forces.  You  are  all  familiar  with  the  fluctuation  of  opinion  on  this  point. 
During  the  first  half  of  the  nineteenth  century  chemists  came  gradually 
to  a  pretty  general  agreement  that  the  atomic  forces  are  electrical  in  their 
nature.  Then  came  the  discovery  of  the  substitution  of  chlorine  for  hy- 
drogen in  organic  compounds  and  the  overthrow  of  the  old  dualistic, 
electrochemical  theory.  Then  for  several  decades  the  question  of  any 
connection  between  electrical  and  atomic  forces  was  generally  ignored 
and  the  attractions  of  the  atoms  were  considered  as  direct  and  positive, 
though,  of  course,  specific  in  character.  During  the  last  twenty  years, 
as  the  theory  of  Arrhenius  with  regard  to  electrolytic  dissociation  or 
ionization  has  come  into  quite  general  favor,  many  different  writers  have 
proposed  theories  which  identify  atomic  attractions  with  electrical  forces. 
Faraday's  law  and  the  whole  group  of  phenomena  which  find  their  most 
satisfactory  explanation  in  the  theory  of  ionization  point  very  strongly 
toward  an  intimate  relation  between  the  two  in  the  case  of  electrolytes. 
But  if  we  assume  that  the  forces  which  hold  atoms  together  in  electrolytes 
are  electrical  it  is  difficult  to  escape  from  the  conclusion  that  the  forces 
are  electrical  in  the  molecules  of  non-electrolytes  also,  for  the  two  classes 
pass  over  into  each  other  so  gradually  that  it  is  very  hard  to  believe  that 
after  the  line  is  passed  we  are  dealing  with  a  radically  different  kind  of 
atomic  force.  Further  than  this,  an  electrolyte  may  be  formed  in  many 
cases  by  two  different  processes,  by  double  decomposition  in  solution  and 
by  the  direct  union  of  the  elements.  Hydrochloric  acid,  acetylene  and 
probably  methane  (from  zinc  methyl  and  by  direct  union  of  carbon  and 
hydrogen)  may  be  cited  as  illustrations.  The  nature  of  the  compounds 
does  not  seem  to  depend  at  all  on  whether  they  are  formed  by  the  one 
process  or  by  the  other. 

The  idea  that  organic  reactions  are  all  ionic  in  character  enables  us, 
also  to  understand  many  reactions  not  so  easily  understood  otherwise. 
Thus  ethyl  alcohol  gives  with  phosphorus  pentachloride,  chlorethane, 
while  phenol  gives  with  the  same  reagent  partly  chlorobenzene,  partly 
phenyl  phosphate.  If  we  assume,  as  seems  natural,  that  ethyl  alcohol 
ionizes  to  ethyl  and  hydroxyl  while  phenol  ionizes  partly  in  the  same 
way  but  chiefly  to  hydrogen  and  phenoxy  ions  these  reactions  become 
clear  : 


4C2H5+  +  3OH-  +  0—  +H++P+++++  +  5C1-  =  4C2H5C1  +  HSP 
or 

4C2H5++4OH-  +  PC1++++  +  4C1-  =  4C2H5C1  +  PC1(OH)4 
PC1(OH)4  =  H3PO4  +  HC1 

3C6H50-  +  3H+  +  C6H5+  +  O—  +  H+  +  P+++++  +  5C1-  = 

C6H5C1+(C6H5)3P04+4HC1. 

If  we  accept  the  reasons  given  and  identify  atomic  and  electrical  forces 
we  have  still  the  question  as  to  the  real  nature  of  these  forces,  for  after 
we  have  called  them  electrical  and  even  after  we  have  identified  them, 
perhaps,  as  residing  in  electrons  (Faraday's  law  and  many  other  things 
point  that  way)  we  still  have  the  inherent  difficulty  of  conceiving  an  at- 
traction existing  between  bodies  at  a  distance  without  a  medium  and  I 
can  not  help  a  strong  belief  that  we  must  ultimately  have  a  theory  for 
the  attractions  as  an  effect  produced  by  the  motions  of  the  electrons. 

ii 


137 1  MOLECULAR   REARRANGEMENTS. 

Such  a  belief  need  not  interfere  with  our  use  of  the  idea  of  positive  and 
negative  charges  as  a  convenient  present  hypothesis.  It  may,  perhaps, 
help  us  to  a  theory  with  regard  to  a  reversal  of  the  charge  which  it  seems 
necessary  to  assume  in  certain  cases  and  which  has  led  to  Abegg's  theory  of 
normal  and  contravalences.  The  hypothesis  proposed  by  J.  J.  Thompson1 
that  combination  is  caused  by  the  transfer  of  negative  corpuscles  from 
one  atom  to  another  has  much  in  its  favor  but  it  assumes  inherent  at- 
tractions between  negative  corpuscles  and  positive  atoms  or  parts  of 
atoms.  Although  the  distances  are  small  such  attractions  are  in  as 
much  need  of  further  explanation  as  is  the  force  of  gravity.  We  assume 
that  the  attractions  and  repulsions  between  conductors  conveying  currents 
or  between  magnets  are  due  to  motions  in  the  ether  between  them.  Is  it 
not  possible  that  the  attractions  and  repulsions  between  corpuscles  and 
atoms  amy  be  explained  in  a  similar  manner? 

The  third  and  last  question  which  I  wish  to  raise  is  as  to  the  nature  of 
the  forces  which  atoms  already  combined  with  other  atoms  exert  in  the 
attraction  or  repulsion  of  still  other  atoms.  Are  these  residual  forces 
merely  the  same  forces  which  hold  the  atoms  in  combination  still  acting 
past  those  atoms  which  are  nearest  and  upon  others  further  away  or  are 
they  different  forces — as  seems  to  be  implied  rather  indefinitely  in  the 
"partial  valences"  of  Thiele?  The  former  idea  seems  simpler  and  more 
logical.  This  question  is  intimately  associated  with  the  mechanism  of  chem- 
ical reactions,  the  causes  for  the  stability  or  instability  of  compounds  and 
especially  with  questions  of  molecular  rearrangements.  As  illustrations 
of  facts  requiring  an  explanation  by  a  more  intimate  knowledge  of  forces 
of  this  sort  we  may  cite  the  stability  of  the  union  of  carbon  with  carbon 
in  ethane  as  compared  with  oxalic  acid,  in  propionic  and  butyric  as  com- 
pared with  malonic  and  acetoacetic  acids  and  in  the  esters  of  these  acids 
as  compared  with  the  free  acids,  in  benzoic  acid  as  compared  with  2,6- 
dimethyl-4-aminobenzoic  acid  (Am.  Chem.  J.,  20,  813  (1898))  in  hydro- 
cinnamic  as  compared  with  phenyl  propiolic  acid  and  in  acetic  as  compared 
with  trichloracetic  acid.  The  instability  of  compounds  similar  to  those 
mentioned  has  long  been  accepted  as  an  empirical  fact  and  it  is  easy  to 
predict  many  cases  where  such  instability  will  occur  but  the  reason  for 
the  instability  has  scarcely  been  discussed.  With  one  exception  the 
separation  always  occurs  between  two  carbon  atoms,  one,  at  least,  of 
which  is  united  to  a  group  or  atom  commonly  designated  as  negative; 
and  the  exception  may  be  only  apparent,  for  the  decomposition  of  2,6- 
dimethyl-4-aminobenzoic  acid  takes  place  in  an  acid  solution  in  which 
the  amino  group  is  combined  with  hydrochloric  acid  and  may  be  con- 
sidered negative. 

It  is  very  noticeable  that  acetoacetic  acid,  CH3COCH2CO2H,  is  much 
less  stable  than  pyrotartaric  acid,  CH3COCO2H.  This  is  some  slight 
indication  that  the  separation  of  the  carbon  atoms  is  ionic  in  character, 
taking  place  more  readily  when  there  is  a  greater  contrast  between  the 
atoms  united  together.  It  may  be  that,  in  this  connection,  we  have 

1  "The  Corpuscular  Theory  of  Matter,"  p.  126.  See  also  the  recent  discussion  by 
Falk,  School  0}  Mines  Quarterly,  30,  179  (1909).  My  own  discussion  of  the  reaction 
between  chlorine  and  ammonia,  THIS  JOURNAL,  23,  460(1901),  also  has  an  important 
bearing  on  Thompson's  hypothesis  of  the  transfer  of  electrons  in  the  union  of  atoms  of 
the  same  element,  Loc.  cit.,  p.  127. 

12 


ORGANIC   AND    BIOLOGICAL,. 


1372 


not  sufficiently  considered  the  difference  between  stability  and  reactivity. 
Thus  sodium  chloride  and  sodium  nitrate  are  both  instantaneously  re- 
active in  solutions,  separating  between  the  sodium  and  the  chlorine  or 
the  sodium  and  the  nitrate  group  but  when  heated  the  former  compound 
is  extremely  stable  while  the  latter  decomposes  between  the  nitrogen 
and  oxygen  rather  than  between  the  sodium  and  the  nitrate  group. 

This  leads  me  to  the  consideration  of  some  of  those  molecular  rearrange- 
ments in  which  I  have  been  especially  interested.  When  camphor  is 
heated  with  phosphorus  pentoxide  it  gives  cymene. 


CH, 


CH, 


-CO 


CH3  —  C  —  CH3 


CH, 


-CH- 


-CH, 


CH3 

CH  —  C  —  CH 

II  I 

CH  —  C  =  CH 


CH3  —  CH  —  CH3 


H,O. 


The  two  carbon  atoms  which  separate  from  each  other  in  this  rearrange- 
ment bear  the  same  relation  to  the  carbonyl  group  as  do  the  two  carbon 
atoms  which  separate  in  either  the  acid  or  ketonic  decomposition  of 
acetoacetic  ester.  This  primary  separation  of  carbon  from  carbon  is  fol- 
lowed by  the  wandering  of  four  hydrogen  atoms,  two  of  these  leaving 
the  molecule  entirely  with  the  oxygen. 

When  camphor  is  heated  with  sulphuric  acid  it  undergoes  a  different 
rearrangement,  giving  £-acetyl-o-xylene  (Armstrong  and  Kipping,  /. 
Chem.  Soc.,  63,  81). 


CH, 


CH 


CH2- 


CH, 


-c- 


-CO 


CH, 


CH, 


-CH- 


-CH2 


CH 


CH 

II 
C-CH, 

C  — CH, 


4H. 


Here  the  rearrangement  is  much  more  complex  and  we  must  assume 
two  primary  separations  of  carbon  atoms,  both  of  which  are  again  in  the 
same  relation  as  before  to  the  carbonyl  group.  We  have  then  a  different 
carbon  atom  uniting  with  one  of  those  which  has  separated,  forming  a 
six- ring  and  a  transfer  of  a  methyl  group  from  one  carbon  atom  to  another, 
a  transfer  that  has  been  noticed  so  many  times  in  other  compounds  that 
it  can  no  longer  be  considered  abnormal.  Four  hydrogen  atoms  are  lost 
but  it  is  not  necessary  to  consider  that  more  than  one  hydrogen  atom 
has  wandered  within  the  molecule. 

When  either  dihydrohydroxycampholytic  acid  or  a-campholytic  acid 
is  allowed  to  stand  for  a  short  time  with  dilute  sulphuric  acid  (i  :  i) 
it  is  transformed  into  /?-campholytic  acid. 


CH, 


-C— CH3 

II 
CH 


CO2H— CH— CH2 
a-Campholytic  acid. 


CO2H- 

j9-Campholytic  acid. 


1373 


MOLECULAR   REARRANGEMENTS. 


If  /3-campholytic  acid  is  allowed  to  stand  with  concentrated  hydro- 
bromic  acid  it  passes  back  to  the  hydrobromide  of  d/-a-campholytic 


acid  : 


/ 


CH8 
CH 


CO,H— C- 


CH2 
-CH, 


Vxiio\ 

>< 

CH/ 
CO2H—  ( 

/CH3 

•v              Q/ 

CH2 
^H  —  CH2 

/?-Campholytic  acid.  dZ-Hydrobromide  of  a-<5ampholytic  acid. 

The  latter  compound  may  lose  hydrobromic  acid  and  give  dl-a-cam- 
pholytic  acid,  or  it  may  exchange  its  bromine  for  hydroxyl  giving  dl-a- 
hydroxydihydrocampholytic  acid  (Walker  and  Cormack,  /.  Chem.  Soc., 
77,  380;  Noyes  and  Blanchard,  Am.  Chem.  J.,  36,  285 ;  Noyes  and  Patterson, 
Ibid.,  27,  426). 

In  both  of  these  transformations  the  methyl  group  separates  from  a 
carbon  atom  adjacent  to  a  carbon  atom  which  is  doubly  united  to  a  third, 
just  as  in  the  acetoacetic  ester  the  separation  is  from  a  carbon  atom  adjacent 
to  one  which  is  doubly  united  to  oxygen.  A  similar  relation,  but  with 
some  variation  is  found  in  the  transformation  of  the  nitroso  derivative 
of  the  anhydroaminolauronic  acid  to  laurolene  (Noyes  and  Derick,  /.  Am. 
Soc.,  31,669(1909)). 

CH3  CH, 

^C 


CH,— O 


CH2. 


H 


HNO 


CH8— CH— CH3 


Here  the  carbonyl  group  leaves  (as  carbon  dioxide)  a  carbon  atom 
attached  to  another  which  is  united  only  to  carbon.  Doubtless  the 
vibrations  set  up  in  the  molecule  at  the  moment  of  decomposition  are  an 
important  factor  in  this  rearrangement. 

The  pinacone-pinacolin  rearrangement  is,  perhaps,  the  first  of  this 
type  which  was  studied. 

OH 

CH,\ 

5i±    CH3^c— co— CHS. 

CH/ 

Tiffeneau  and  his  collaborators  have  recently  studied  very  many  re- 
arrangements similar  to  these,  phenyl  and  other  groups  as  well  as  methyl 
being  transferred  in  many  cases. 

These  shiftings  of  groups  seem  to  take  away  from  under  us  one  of  the 
most  important  principles  on  which  we  rely  for  the  determination  of 
structure,  the  principle  that  groups  of  atoms  pass  from  one  compound 
to  another  without  changing  their  mutual  relations.  But  when  we  think 
of  the  matter  a  little  further  we  see  that  in  all  chemical  reactions  we 
expect  the  atoms  to  separate  from  each  other  at  some  point,  and  the  only 
thing  which  surprises  us  is  that  a  separation  has  taken  place  at  a  point 


ORGANIC   AND   BIOLOGICAL.  1374 

where  we  did  not  expect  it.  We  can  already  see  some  empirical  relations 
between  the  compounds  in  which  these  separations  and  rearrangements 
take  place  and  can  predict  to  a  certain  extent  where  they  are  liable  to 
occur.  But  we  are  still  wholly  in  the  dark  as  to  the  real  forces  which 
lie  behind  and  are  the  cause  of  the  transformations. 

J.  J.  Thomson,  Rutherford  and  others  have  shown  that  in  the  phe- 
nomena of  conductivity  of  gases  and  of  radioactivity  we  have  new  and 
most  powerful  means  of  studying  the  properties  of  matter  and  energy 
which  have  thrown  a  flood  of  light  upon  the  nature  of  atoms.  Ostwald 
at  the  other  extreme  has  wished  to  discard  atoms  altogether  and  to  explain 
structural  organic  chemistry  on  the  basis  of  thermodynamics.  Richards, 
from  a  somewhat  intermediate  point  of  view  but  with  distinctly  more 
sympathy  with  Ostwald  than  with  Thomson,  has  given  us  a  conception  of 
compressible  atoms  which  is  surprisingly  like  the  latter's  corpuscular  theory 
of  chemical  combination  as  developed  in  his  latest  book.  Michael  wishes 
to  explain  phenomena  of  this  sort  by  the  law  of  entropy.  Thiele,  imbued 
with  the  ideas  of  structure,  explains  them  in  part  by  partial  valences. 
Still  others  have  attempted  to  study  such  problems  from  the  properties 
of  crystals,  the  absorption  of  light,  and  a  great  variety  of  other  phenomena. 
The  great  number  of  properties  which  must  finally  be  coordinated  in 
any  true  explanation  of  atomic  and  molecular  forces  is  discouraging  and 
gives  some  basis  for  that  agnostic  point  of  view  which  considers  the 
number  of  possibilities  infinite  and  that  we  can  never  hope  for  a  knowl- 
edge of  the  truth  even  as  to  the  existence  of  atoms.  Let  us  rather  take 
the  more  hopeful  view  that  some  one,  in  a  not  too  distant  future,  will 
give  us  a  simple  and  comprehensive  theory  of  the  nature  of  atoms  and  of 
the  forces  which  bind  them  together  in  compounds.  The  one  who  is 
to  do  this  must  not  look  at  science  as  cut  up  into  water-tight  compart- 
ments but  must  be  able  to  coordinate  the  evidence  which  conies  from 
workers  in  many  diverse  fields  of  chemistry,  of  physics  and  of  other 
sciences. 

URBANA,  ILL. 


ORGANIZATION  OF  INDUSTRIAL  RESEARCH.1 

BY  WILLIS  R.  WHITNEY. 
Received  November  6,  1909. 

The  intimate  connection  between  the  purely  scientific  research  of  a 
people  and  its  advance  in  the  art  of  good  living  cannot  be  too  frequently 
discussed.  The  organization  of  industrial  research  involves  arranging 
and  maintaining  a  body  of  involute  parts  as  an  operative  whole  of  high- 
est efficiency.  It  is  never  perfectly  accomplished,  and  the  fact  that 
improvement  can  always  be  made  is  an  incentive  for  its  discussion. 

A  recent  copy  of  Life  has  this  to  say,  which,  without  straining,  bears 
direct  upon  industrial  research: 

"This  is  the  most  interesting  country  in  the  world.  The  game  here 
is  the  biggest  that  is  being  anywhere  played.  The  problems  of  humanity 
that  are  being  worked  out  here  are  the  greatest  problems  under  considera- 
tion, and  the  prospect  of  solving  them  is  better  than  it  is  anywhere  else." 

Lord  Bacon  said:  "The  real  and  legitimate  goal  of  the  sciences  is  the 
endowment  of  human  life  with  new  invention  and  riches."  He,  in  turn, 
cited  King  Solomon,  who  said,  "it  is  the  glory  of  God  to  conceal  a  thing, 
but  the  glory  of  a  king  to  search  it  out." 

Bacon  distinguishes  three  degrees  of  ambition: 

First,  that  of  men  anxious  to  enlarge  their  own  power  in  their  own  coun- 
try. This  is  "vulgar  and  degenerate." 

Second,  that  of  men  who  strive  to  enlarge  the  power  and  empire  of 
their  country  over  mankind.  This  is  "more  dignified,  but  not  less  covet- 
ous." 

Third,  that  of  those  who  strive  to  enlarge  the  power  and  empire  of 
mankind  in  general  over  the  universe.  Evidently  this  is  the  best,  and 
is  the  real  ambition,  whether  recognized  or  not  by  himself,  of  any  good 
experimenter. 

For  purposes  of  systematic  analysis,  the  subject,  "Organization  of  In- 
dustrial Research,"  may  be  divided  into  two  parts: 

Part  one,  the  personal  or  mental  organization,  with  its  requirements, 
etc. 

Part  two,  the  objective  or  material  organization. 

For  brevity,  these  may  be  called  the  mind  and  the  matter  organiza- 
tions. 

The  former,  or  personal,  I  will  subdivide  into  such  parts  as: 

Its  training  and  characteristics. 

Division  of  its  labors. 

Its  records,  etc. 

The  objective  or  matter  organization,  I  divide  into : 

1  An  address  delivered    at    the    Twentieth  Anniversary    of   Clark    University, 
Worcester,  Mass.,  Sept.  17,  1909. 

16 


GENERAL,    PHYSICAL  AND   INORGANIC.  72 

The  fields  for  material  research. 

The  laboratory  equipment  and  systems  of  its  material  co-operation. 

Naturally,  the  personal  comes  first,  relatively  and  chronologically, 
and  the  mental  precedes  the  material.  The  personal  factor  is  everything 
in  industrial  research.  Strangely  enough,  it  is  everywhere  and  always 
dominant,  while  every  other  factor  is  sometimes  recessive.  In  an  organ- 
ization "A"  cannot  work  well  with  "B"  because  one  is  too  slow,  too 
fast,  to  egotistical,  too  jealous,  too  narrow,  etc.  Nowhere  else  do  the 
personal  traits  protrude  so  much  as  in  concerted  research.  And  so  I 
hold  that  above  all,  as  an  industrial  experimenter,  I  should  like  as  broad 
a  human  training  as  possible,  before  any  other  specific  one.  This  proba- 
bly means  little  more  than  acquirement  of  a  demonstrated  desire  to  play 
fair,  and  it  may  be  no  more  applicable  to  this  field  than  to  others. 

To  one  always  in  close  touch  with  research,  it  seems  as  though  there 
is  an  immutable  law  of  nature  which  may  be  stated  as  follows:  (It  is 
an  application  of  the  principle  of  reversible  reactions  so  as  to  include  the 
reactions  of  the  mind.) 

The  equilibrium  between  mental  and  material  conception  is  so  sensi- 
tive that  anything  which,  to  the  fair  mind,  seems  possible,  is  to  the  trained 
persistence  permissible.  If  this  should  be  proven  not  strictly  true,  it 
would  still  be  a  good  working  hypothesis  for  a  research  organization. 

This  theory  requires,  then,  a  certain  characteristic  in  the  generally 
successful  research  operator.  This  is  recognized  in  optimistic  activity 
and,  to  my  mind,  should  be  placed  first  among  the  requisites.  It  is  placed 
above  knowledge,  because,  without  it,  little  that  is  new  will  ever  be  done 
except  by  accident.  With  active  optimism,  even  in  absence  of  more 
than  average  knowledge,  useful  discoveries  are  almost  sure  to  be  made. 

Speaking  from  personal  analysis  and  from  the  observation  of  others, 
I  would  say  that  general-chemical  and  physical  knowledge  may  some- 
times be  as  much  a  detriment  as  a  help  to  one  imbued  only  with  a  need 
of  solving  new  problems.  A  possible  explanation  is  this:  We  always 
reason  deductively.  We  apply  general  laws  in  attempting  to  answer 
specific  questions.  To  any  specific  problem  of  research  there  are  usually 
general  laws  which  may  seem  to  forbid  the  solution.  These  laws  are 
known  and  revered.  Naturally,  the  unknown,  specific  ways  by  which 
it  may  be  solved  are  more  or  less  hidden.  An  illustration  may  not  be 
out  of  place  here : 

Cotton  may  be  dissolved  in  a  solution  of  zinc  chloride.  The  solution 
may  be  squirted  through  a  die  into  alcohol  in  such  a  way  that  a  smooth, 
coagulated  cellulose  thread  is  thereby  obtained.  This  may  be  heated 
so  as  to  give  a  solid,  compact  and  pure  carbon  filament.  Many  are  thus 
made.  But  as  a  new  problem,  it  would  certainly  appear  quite  imprac- 
ticable to  one  who  might  have  a  fairly  extensive  knowledge  of  the  chem- 
istry of  the  materials.  Generally  speaking,  zinc  chloride  solution  does 
not  dissolve  cellulose.  Only  a  strong  solution,  kept  at  a  high  temperature 
for  a  long  time,  will  give  the  desired  solution.  In  general,  too,  it  could 
not  be  squirted  and  coagulated  into  a  smooth  thread.  Very  specific 
conditions  are  necessary.  Finally,  the  treatment  with  gradually  rising 
temperature,  which  alone  succeeds  in  giving  the  compact  carbon  fila- 
ment, is  a  matter  of  specific  detail.  The  places  in  this  process  where 
general  reasoning  points  to  failure  are  numberless.  Years  of  multiplied 
effort  are  necessary  to  perfect  such  a  process.  Once  established,  it  is 

17 


73  ORGANIZATION   OF   INDUSTRIAL  RESEARCH. 

easily  analyzed  along  the  lines  of  understood  reason  and  theories  of  re- 
actions may  be  based  upon  the  facts.  But  such  processes  are  not  laid 
out  greatly  in  advance  of  their  accomplishment.  The  successful  steps 
are  found  among  the  many  which  are  actually  attempted,  and  something 
more  than  general  knowledge  is  necessary.  This  something  is  hopeful 
pertinacity,  optimistic  activity.  To  a  chemist  imbued  with  fair  knowl- 
edge, it  was  recently  apparently  useless  to  attempt  such  an  experiment 
as  the  continual  removal  of  traces  of  hydrogen  from  oxygen  by  passing 
the  gas  through  a  red-hot  iron  pipe.  He  had  seen  iron  wire  burned 
rapidly  in  oxygen,  he  tried  wrought  iron  and  the  iron  was  oxidized,  and 
his  knowledge  was  vindicated,  but  he  also  tried  cast  iron  and  found  that 
it  did  not  burn  and  that  it  would  operate  perfectly.  A  scramble  for  an 
explanation  evolved  the  theory  that  the  silicon  burning  to  silica  protected 
the  iron.  Ex.  postfacto  theories  are  permissible. 

As  the  mental  world  is  constituted,  optimists  are  greatly  in  the  minority, 
when  one  counts  those  only  who  are  also  imbued  with  knowledge.  There- 
fore, in  practice,  the  optimist  must  be  used  to  crystallize  the  efforts  of 
others  less  optimistic.  Thus,  any  large  industrial  research  laboratory 
is  soon  perforce,  systematized  into  organized  clusters  of  people,  working 
along  distinct  and  different  lines.  This  permits,  in  our  case,  of  the 
combined  use,  to  maximum  efficiency,  of  the  delicate  hands  of  young 
women,  the  strength  and  skill  of  trained  mechanics,  the  mind  of  the  use- 
ful dreamer,  the  precision  and  knowledge  of  the  skilful  chemist,  and  the 
data  of  the  accurate  electrical  engineer. 

Simple  mathematical  axioms  make  clear  the  fact  that  a  group  of  opera- 
tors working  together  on  a  subject,  are  related  to  the  same  group  opera- 
ting separately,  as  a  power  is  related  to  a  simple  sum.  This  principle 
holds  as  well  among  a  group  of  groups  and  to  related  subjects.  It  is  evi- 
dent, for  example,  that  knowledge  gained  along  the  line  of  insulation 
would  be  of  use  in  a  study  of  conduction,  and  that  the  man  who  had 
studied  the  reduction  of  tungstic  oxide  by  carbon  in  vacua  could  help 
the  one  who  is  working  with  a  pressure  furnace,  upon  the  equilibrium 
between  carbon  monoxide  and  carbon  dioxide.  Therefore,  the  strength 
of  a  research  department,  properly  operated,  should  rise  exponentially 
with  its  numbers. 

To  this  audience,  the  importance  of  highest  advance  in  specific  chem- 
ical and  physical  training  will  probably  be  apparent,  but  an  expression 
of  it  may  be  of  use.  The  supply  of  highly  trained  men  is  below  the  de- 
mand. There  is  a  healthy  supply  of  moderately  trained  men.  This 
applies  to  all  general,  scientific  training.  Let  me  give  more  concrete 
ideas.  There  are  a  hundred  chemists  who  can  fill  satisfactorily  an  analyst's 
position,  to  one  who  knows  what  J.  J.  Thomson  has  done  or  who  reads 
Drude's  Annalen.  Reading  the  Annalen  is  not  a  "sine  qua  non,"  but  it 
is  an  indicator  of  no  little  merit.  If  a  chemist  or  a  physicist  is  not  suffi- 
ciently interested  to  keep  informed,  he  is  probably  not  going  to  work  at 
high  efficiency  as  an  investigator.  This  does  not  preclude  the  possibility 
of  splendid  research  work  being  done  by  some  one  who  is  confined  to  a 
very  limited  field  of  vision,  but  such  cases  are  the  exception  and  cannot 
be  used  as  bases  for  common  application.  In  general,  the  man  with  the 
best  tools  and  with  the  best  knowledge  and  experience  in  their  use,  will 
advance  most  rapidly  in  industrial  research.  In  my  own  experience, 
we  frequently  have  a  line  of  work  which  demands  the  addition  to  the 

18 


GENERAL,    PHYSICAL   AND   INORGANIC.  74 

force  of  well  trained  men.  The  difficulty  which  stands  out  most  mark- 
edly when  considering  this  problem  is  usually  the  scarcity  of  men  who 
are  highly  enough  trained  along  the  line  of  pure  research.  While  in  many 
fields  of  industrial  research  new  and  brilliant  discoveries  will  continue 
to  be  made  suddenly  and,  as  it  were,  out  of  new  cloth,  still  many  more 
are  being  made  by  the  most  careful  application  of  highly  refined  methods 
and  knowledge,  to  processes  which  already  seem  at  first  pretty  well  worked 
out.  This  intensive  farming  is  most  promising  and  demands  the  highest 
skill.  It  is  to-day  most  difficult  to  find  American  trained  men  who  can 
do  this  work.  It  is  a  German  attribute  which  we  would  do  well  to  make 
our  own. 

If  the  chemist  is  only  a  chemist  or  the  physicist  confined  to  pure  physics, 
he  is  liable  to  overestimation  of  the  laws  he  learns.  He  should  be  some- 
thing of  a  "mental  mixer,"  one  who  has  enough  history,  enough  psy- 
chology, and  enough  faith  to  read  possibility  of  acquirement  for  the  future 
out  of  knowledge  of  attainments  in  the  past. 

As  we  have  said,  one  of  the  most  practical  detriments  to  successful 
industrial  research  is  that  automatic  action  of  the  mind  which  recognizes 
the  possible  grounds  for  a  failure  quicker  than  it  sees  the  probable  ways 
to  success.  Research  needs  more  aviators.  Those  of  us  who  feel  the 
work-horse  brand  on  our  work  have  a  call  to  cultivate  a  flying  spirit, 
and  are  to  be  condemned  only  if  we  stand  still. 

In  this  connection,  I  am  in  favor  of  anything  which  helps  train  the 
American  student  in  the  path  of  sanguine  research.  It  can  be  done  Jay 
research  men  themselves,  but  probably  not  by  others.  It  is  not  the 
knowledge  which  the  student  preparing  for  research  needs,  so  much  as  the 
spirit  of  the  investigator.  His  thoughts  should  not  be  fettered  by  laws, 
but  helped  by  them  to  fly.  This  can  be  done  best  by  those  who  are  opti- 
mistic almost  to  the  extinction  of  reason. 

A  search  in  the  research  laboratories  of  the  world  to-day  would  dis- 
close large  numbers  of  J.  J.  Thomson  men,  Ostwald  men,  Nernst  men, 
van't  Hoff  men.  The  teacher  probably  made  the  school.  The  investi- 
gator probably  endowed  the  students,  not  with  facts  alone,  but  with 
spirits.  We  are  not  of  that  hopeless  class  who  assume  that  the  sparks 
of  genius  are  only  Heaven-sent,  but  we  are  inclined  to  adopt  as  an  axiom 
that  man  is  flexible,  auto-corrigible  and  mentally  elastic  beyond  limit. 
Therefore  the  rare  genius  in  research,  as  elsewhere,  is  the  one  most  given 
to  hopeful  effort. 

To  dwell  for  a  moment  upon  points  in  a  system  for  co-operation  of  a 
research  force,  I  will  describe  our  own  scheme. 

The  present  corps  comprises  about  eighty  people,  about  thirty  of  whom 
are  college  men,  mostly  chemists.  Every  man  or  woman  on  the 
research  staff  is  expected  to  give  undivided  effort  to  the  work. 
Whatever  invention  results  from  his  work  becomes  the  property  of 
the  company.  I  believe  that  no  other  way  is  practicable.  An  attempt 
to  reward  systematically  such  labors  by  a  scheme  of  royalty  payment 
is  more  impracticable  than  the  operation  of  a  manufacturing  plant  upon 
a  graded  scheme  of  profit  sharing.  In  this  case  an  immediate  and  fairly 
equitable  division  of  profits  is  sometimes  possible.  In  research,  the 
problem  itself  is  an  asset  of  the  organization.  Both  the  equipment 
and  the  risks  belong  to  the  organization.  The  accumulated  experience 
of  the  force  as  a  whole  is  its  property.  Finally,  the  privilege  of  direct- 

19 


75  ORGANIZATION   OF  INDUSTRIAL  RESEARCH. 

ting  the  work  of  operators  along  lines  where  no  direct  financial  benefit 
(or  an  immeasurable  one)  to  the  company  could  ever  be  determined, 
must  belong  to  it.  Every  operator  is  expected  to  keep  good  notes  and 
his  books  become  a  part  of  the  laboratory  files.  In  most  cases  weekly 
typewritten  reports  are  made  by  each  worker,  and  copies  of  these  also 
become  part  of  accessible  library  files.  For  purposes  of  establish- 
ment of  dates,  etc.,  witnesses  who  read  and  understand  the  notes  also 
endorse  them.  Photographs  of  apparatus,  curves,  etc.,  are  frequently 
added  wherever  useful,  and  each  room  of  the  laboratory  is  photographed 
regularly  and  the  dated  photographs  are  bound  in  books,  to  record  stand- 
ing conditions.  Wherever  practicable,  single  sheets,  of  standard  reporr 
size,  are  printed  to  cover  oft-repeating  data,  so  that  the  experimenter 
regularly  fills  in  certain  blanks,  as,  for  example,  in  experiments  on  carbon 
motor  brushes:  the  composition  of  the  particular  lot,  temperature  and 
time  of  drying  and  firing,  hardness,  resistivity,  tensile  strength,  and  all 
other  tests  of  the  product.  The  use  of  plotted  curves  on  standard  milli- 
meter paper,  for  use  where  one  property  of  material  is  studied  as  a  func- 
tion of  some  other  variable,  is  very  common  in  our  reports.  This  occurs, 
for  example,  in  practically  all  cases  where  electric  furnace  work  is  de- 
scribed, and  where  the  changes  undergone  by  incandescent  lamps  during 
their  life  are  recorded. 

These  conditions  are  the  result  of  eight  years  of  development.  The 
system  has  been  subjected  to  many  changes  and  may  still  be  greatly  im- 
proved. It  is  possible  to  have  such  a  complex  system  of  record  that 
efficiency  is  sacrificed.  We  have  reached  the  present  stage  because  of 
frequent  indications  of  previous  weakness  in  the  simpler  methods.  Very 
few  good  investigators  can  keep  good  notes.  The  more  interested  the 
investigator  becomes,  the  more  difficult  it  seems  for  him  to  carefully 
record  his  passing  work.  His  eyes  and  mind  are  always  upon  the  ex- 
citing and  more  interesting  advance.  It  seems  not  so  tempting  to  actually 
make  history  by  the  writing  as  to  metaphorically  make  it  by  the  concep- 
tion or  experiment. 

We  now  come  to  the  material  side  of  the  subject. 

In  the  early  days,  the  same  hands  which  mined  the  iron  ore  and  operated 
the  bellows,  also  forged  the  sword  and  plowshare  and  touched  the  goods 
which  were  the  equivalent  in  exchange.  The  records  of  the  development 
through  which  the  distribution  of  the  steps  of  such  processes  has  gone  is 
what  we  call  the  history  of  man.  It  is  not  always  easy  to  recognize  the 
extent  to  which  this  development  is  progressing  in  our  own  time.  Sta- 
tistics ought  to  show  us,  but  these  often  fail  to  impress  us.  It  may  be 
that  if  used  to  a  limited  extent  to  armor  an  argument,  a  few  data  will  be 
of  interest  in  connection  with  industrial  research. 

The  known  chemical  compounds  of  the  earth  are  myriads.  The  still  un- 
known, but  knowable,  are  certainly  many  myriads  more,  but  any  consid- 
eration of  either  great  mass  is  too  huge  a  task.  We  may,  however,  con- 
sider for  a  moment  a  part  of  the  alphabet  from  which  that  language  is 
made.  We  will  consider  research  as  applied  to  the  metallic  elements  alone. 

There  are  about  75  elements.  About  two-thirds  are  metals.  Of  these, 
only  a  very  few  can  be  said  to  have  been  the  subject  of  much  industrial 
research.  It  is  impossible  to  accurately  measure  the  extent  to  which  an 
element  has  been  studied  with  a  view  to  its  possible  use  by  the  race,  but 
we  have  no  difficulty  in  recognizing  that  iron  and  copper  have  been  much 

20 


GENERA!,,    PHYSICAL  AND  INORGANIC.  76 

studied,  while  calcium  and  silicon  have  not.  In  these  illustrations  we  have 
not  selected  rare  elements.  The  calcium  and  silicon,  which  have  been  least 
used  by  man  thus  far,  are  more  common  than  copper  or  iron.  A  natural 
explanation  of  the  lack  of  development  of  such  elements  is  a  lack  of  need, 
but  this  is  possibly  incorrect.  Copper,  iron,  etc. ,  were  certainly  first  obtained 
by  accident  as  distinct  from  design.  The  uses  to  which  they  could  be  put 
were  later  developed  by  trial.  The  finding  of  some  uses  established  the 
further  supply,  which  insured  the  subsequent  discovery  of  new  uses.  This 
mirrors  the  history  now  being  made  by  new  elements  such  as  silicon. 
Only  in  the  past  year  the  commercial  production  of  this  element  has  been 
begun,  and  about  500  tons  were  sold  for  a  deoxidizer  in  steel-making. 
Thus  a  substance  absolutely  out  of  reach  of  almost  every  chemist  a  few 
years  ago,  can  now  be  obtained  as  cheaply  as  zinc. 

Similarly,  future  needs,  which  only  calcium,  for  example,  can  meet, 
are  certain  to  be  developed.  More  calcium  will  then  be  made.  The  cost 
of  production  will  be  reduced  and  the  field  of  its  usefulness  will  again 
and  ever  afterward  continue  to  broaden.  Never  in  the  history  of  the 
world  has  the  rate  of  iron  production  been  so  great  as  at  present  (nearly 
two  million  tons  a  month  by  the  U.  S.  Steel  Company  alone).  Copper  is 
being  mined  more  rapidly  than  ever  before.  We  have  ourselves  seen  the 
industrial  birth  and  growth  of  a  new  metal  which  points  to  the  great 
possibilities  in  case  of  the  other  unused  elements.  I  refer  to  aluminium. 
Only  two  to  three  tons  were  made  as  late  as  1884  while  furnaces  now 
exist  which  are  capable  of  yielding  three  to  four  times  this  quantity  every 
hour  of  the  day  and  night.  Its  present  uses  could  only  have  been,  and 
were,  very  imperfectly  predicted,  before  actual  industrial  research  made 
tentative  use  of  it.  So  it  must  be  with  other  elements.  One  is  not  too 
bold  who  assumes  that  all  the  elements  which  are  found  in  abundance 
will  be  industrially  utilized  when  they  have  been  economically  isolated 
and  thoroughly  investigated. 

I  am  considering  the  metallic  elements  only  in  order  to  point  out  in  a 
concrete  manner  the  need  of  high-quality  research,  physical,  chemical, 
electrical,  etc.,  in  the  simplest  field.  Evidently  this  field,  among  com- 
pounds of  the  elements,  is  again  bounded  only  by  the  infinite.  I  am  im- 
pressed with  the  idea  that  the  commonest  elements  in  nature  have  not 
been  studied  with  anything  like  the  care  which  has  been  given  to  those  for 
which  the  demands  are  already  developed. 

In  our  age,  a  single  investigator  will  probably  not  isolate,  in  large 
quantities,  the  metal  tellurium,  for  example,  and  also  put  it  to  use  to 
fill  one  of  his  individual  needs,  as  did  the  warrior  who  first  fashioned  an 
iron  blade  or  axe.  The  men  who  develop  the  myriad  uses  to  which  the 
common  element  titanium  will  be  put,  will  have  to  rely  upon  the  previous 
work  of  many  investigators.  It  is  in  this  respect  that  the  conditions  are 
continually  changing,  and  always  in  one  direction.  I  call  it  the  direction  of 
specific  complexity.  Our  wants  are  very  complex.  We  are  learning  to 
demand  very  specific  properties.  It  is  this  fact  which  makes  necessary 
the  research  work  of  the  specialist,  the  specific  or  narrow  investigation 
of  the  pure  scientist,  the  pioneer  work  of  the  trail-blazer,  the  crude  and 
hurried  trials  by  the  inventor,  the  long  and  exacting  developments  of 
the  practical  application  in  the  factory,  etc.  Demands  for  new  materials 
do  not  really  precede  the  discovery  of  the  product,  any  more  than  the 

21 


77  ORGANIZATION   OF   INDUSTRIAL  RESEARCH. 

demand  for  high-speed  tool  steel  preceded  the  discovery  of  the  prop- 
erties of  the  chrome-tungsten-iron  alloys.  With  the  material  dis- 
covered, its  properties  known,  the  world  apparently  could  then  hardly 
get  along  without  it.  This  means  that  necessity  is  not  the  mother  of 
invention.  Knowledge  and  experiment  are  its  parents.  It  sometimes 
happens  that  a  successful  search  is  made  for  unknown  material  to  fill 
well  recognized  and  predetermined  requirements.  It  more  often  happens 
that  the  acquirement  of  knowledge  of  the  previously  unknown  properties 
of  a  material  suggests  its  trial  for  some  new  use.  These  facts  strongly 
indicate  the  value  of  knowledge  of  properties  of  materials  and  indicate 
a  way  for  research. 

Among  the  recently  developed  uses  for  modern  metals  which  were 
certainly  not  surmised  until  the  metal  itself  had  been  made  easily  available, 
are  the  use  of  aluminium  and  silicon  as  deoxidizers  in  steel-making,  where 
all  the  silicon  and  a  large  part  of  the  aluminium  are  now  used.  This 
discovery  of  utility  by  experiment,  rather  than  the  discovery  of  material 
by  force  of  necessity,  is  again  illustrated  by  the  metals  titanium  and  vana- 
dium. The  former  is  used  in  arc  lamps  because  it  was  found,  by  experi- 
ment, to  give  a  good  light.  (Your  Worcester  streets  are  lighted  by  it.)  The 
latter  has  been  surprisingly  useful  in  steel-making,  where  a  fraction  of 
i  per  cent,  has  been  found  to  impart  additional  strength  to  the  steel. 
In  this  way,  about  a  thousand  tons  of  vanadium  are  now  used  annually 
in  America. 

When  the  first  step  is  taken  from  the  study  of  the  supply,  production 
and  utilities  of  our  metallic  elements,  the  next  step  is  apparently  along 
the  lines  of  alloys  and  we  readily  see  how  quickly  the  field  widens.  The 
recent  great  advances  in  scientific  foundation  for  much  study  are  to  be 
attributed  to  the  physical  chemists,  to  such  men  as  Tamman  and  his 
school.  In  their  work  we  begin  to  see  the  magnitude  of  the  alloy  field. 
There  are  probably  over  a  thousand  pairs  of  metals  whose  properties  as 
alloys  are  still  absolutely  unstudied,  and  for  alloys  of  three  or  more  metals 
the  number  is  legion. 

It  seems  as  though  our  advance  could  be  quickened  by  a  greater  in- 
timacy with  the  newly  cheapened  elements.  When  sodium,  chlorine, 
bromine,  silicon,  magnesium,  chromium,  cobalt,  manganese,  tungsten,  etc., 
etc.,  are  many  times  as  available  or  cheap  as  they  were  only  ten  years 
ago,  it  is  probable  that  the  possible  uses  are  not  up-to-date. 

The  field  of  material  research  really  divides  into  two  parts:  the  search 
for  more  economical  production  and  the  search  for  wider  application.  These 
two  go  hand  in  hand.  If  the  one  advances,  the  other  is  led  along.  In 
this  way,  in  our  laboratory,  the  knowledge  of  such  elements  as  carbon, 
as  in  its  forms  of  graphite  in  lamp  filaments,  in  motor  brushes,  in  electrodes, 
etc.,  has  been  widely  and  continually  advanced.  The  result  is  not 
a  conclusion  that  we  know  all  about  carbon,  but  rather  that  it  still  pre- 
sents a  wonderful  field  for  useful  research. 

From  the  materials  worked  upon,  to  the  tools  is  a  step.  Our  experience 
here  is  concrete  and  clear,  and  we  want  to  record  our  impressions.  Good 
tools,  new  tools,  rare  tools,  are  most  valuable.  No  good  tool  lives  long 
for  a  single  use  alone.  Many  times  we  have  questioned  the  advisability 
of  installing  some  new  apparatus — a  vacuum  furnace,  a  pair  of  metal  rolls, 
some  special  galvanometer,  some  microscope,  an  hydraulic  press,  a  power 

22 


ORGANIC   AND   BIOLOGIC AL,.  78 

hammer,  a  steam  digester,  etc.,  etc.  Never,  after  it  became  a  part  of  the 
equipment,  has  it  seemed  possible  to  proceed  without  it.  In  the  single 
case  of  the  electric  vacuum  furnace,  for  example,  our  laboratory  has  made 
almost  continual  use  of  from  three  to  eight  for  the  past  five  years.  The 
laboratory,  piped  several  years  ago  with  high  vacuum  and  with  electro- 
lytic hydrogen,  besides  steam,  air,  water  and  gas,  will  probably  never 
operate  without  them. 

Similarly,  this  applies  to  a  library.  In  general,  the  most  useful  and 
fertile  of  our  investigators  use  the  library  the  most.  This  is  as  it  should 
be.  The  recorded  research  work  in  a  library  of  a  few  thousand  volumes 
frequently  represents  the  work  of  millions  of  work-hours,  and  there  is 
little  excuse  for  not  availing  oneself  of  the  published  experience  of  others. 
A  library  containing  ten  of  the  leading  research  journals  of  the  world 
may  be  said  to  have  in  each  volume  about  100,000  available  brain-power- 
hours.  So  a  library  corresponds  to  a  charged  storage  battery  of  great 
capacity. 

RESEARCH  LABORATORY.  GENERAL  ELECTRIC  Co., 

SCHBNBCTADY,   N.  Y. 


THE  ACIDS  OF  THE  PHENYLPROPIOLIC  SERIES  AND  THEIR 
CONDENSATION  TO  NAPHTHALENE  DERIVATIVES.1 

BY  JOHN  E.  BUCHER. 
Received  December  9,  1909. 

In  an  investigation  of  the  action  of  acetic  anhydride  on  acids  of  the 
acetylene  series  in  1895,  Michael  and  Bucher2  obtained  the  anhydride 
of  a  new  acid  from  phenylpropiolic  acid.  Three  years  later,3  after  a 
thorough  study  of  the  compound,  they  proved  it  to  be  the  anhydride  of 
i-phenyl-2,3-naphthalenedicarboxylic  acid.  It  was  found  to  have  the 
composition  corresponding  to  the  formula  C^H^Og  and  a  molecular 
weight  of  274. 

This  corresponds  to  the  composition  of  a  phenylpropiolic  anhydride 
(C8H5.C  H=  C.CO)2O,  but  the  acid  obtained  from  it  was  found  to  be  sat- 
urated and  entirely  different  from  phenylpropiolic  acid.  This  structural 
formula  evidently  does  not  represent  its  constitution. 

It  seemed  probable  that  three  molecules  of  the  acid  might  have 
polymerized  to  triphenyltrimesic  acid  in  a  manner  analogous  to  the  for- 

C.CO2H 


C6H5. 
H03C.cl  Jc.C02H 

C.C8H8 

1  Presented  at  the  Second  Decennial  Celebration  of  Clark  University,  Worcester, 
Mass.,  September  14,  1909. 
7  Ber.,  28,  2511  (1895). 
1  Am.  Chem.  ] .,  20,  89  (1898). 

23 


213 


ACIDS  OF  THE   PHENYLPROPIOLIC  SERIES. 


mation  of  benzene  from  acetylene.  The  resulting  acid  was  found  to  be 
dibasic  and  to  have  only  two-thirds  of  the  required  molecular  weight. 
These  facts  showed  conclusively  that  the  compound  is  not  the  anhydride 
of  triphenyltrimesic  acid. 

It  was  then  thought  possible  that  the  compound  might  be  the  anhy- 
dride of  diphenyltetrenedicarboxylic  acid. 

C8H6.C  r -i  C.C02H 


C,H8.C 


C.CO3H 


This  acid  would  contain  two  carboxyl  groups  in  the  ortho  position  and 
it  would  be  dibasic.  One  might  expect  benzil  among  the  oxidation 
products  of  such  an  acid  but  many  experiments  failed  to  show  the  slightest 
trace  of  this  substance.  It  was  not  possible  to  find  any  evidence  in 
favor  of  the  tetrene  formula. 

As  none  of  these  three  formulas  corresponded  to  the  compound,  it 
was  evident  that  the  polymerization  of  the  phenylpropiolic  acid  must 
have  proceeded  in  a  very  unusual  manner. 


H02C. 
H02C. 


,C.CO2H 
.CO,H 


CH 


24 


ORGANIC   AND    BIOLOGICAL.  214 

They  finally  succeeded  in  isolating  diphenyltetracarboxylic-  and  ortho- 
benzoylbenzoic  acids  from  its  oxidation  products  and  in  preparing  its 
hydrocarbon.  The  hydrocarbon  was  also  oxidized  to  orthobenzoyl- 
benzoic  acid.  The  preceding  formulas  show  these  transformations. 

These  facts  can  only  be  explained  by  the  above  constitutional  formula 
and  the  compound  is  therefore  the  anhydride  of  i-phenyl-2,3-naph- 
thalenedicarboxylic  acid. 

Later,  several  investigators  who  evidently  had  overlooked  the  above  work 
obtained  this  compound.  Basing  their  reasoning  on  insufficient  experi- 
mental evidence,  they  described  the  substance  first  as  the  anhydride  of 
triphenyltrimesic  acid  and  afterwards  as  that  of  diphenyltetrenedicar- 
boxylic  acid,  representing  structural  formulas  which  had  already  been 
shown  to  be  untenable  by  Michael  and  Bucher.  For  example,  Lanser1 
obtained  the  compound  by  heating  phenylpropiolic  acid  with  phosphorus 
oxychloride,  and  assigned  the  formula  C^HgoOg  for  triphenyltrimesic 
anhydride  without  making  molecular  weight  determinations. 

A  little  later  Manthey2  determined  the  molecular  weight  thus  showing 
the  formula  to  be  C18H10OS  and  that  the  constitution  must  be  different 
from  that  assigned  by  Lanser.  This  evidence  together  with  the  fact 
that  the  acid  contains  the  two  carboxyl  groups  in  the  ortho-position, 
led  him  to  assign  the  tetrene  formula. 

In  a  later  paper,  Lanser  and  Halvorsen8  acknowledge  the  correctness 
of  Manthey 's  experimental  work  and  they  also  accept  the  tetrene  formula. 
The  reactions  which  they  study  would,  however,  apply  equally  well  to 
other  ortho-dibasic  acids. 

Ruhemann  and  Meriman4  also  obtained  the  anhydride  in  studying  the 
action  of  phenylpropiolyl  chloride  on  acetone  in  pyridine  solution. 
They  proved  the  identity  of  their  compound  with  that  of  Lanser  and 
regarded  it  as  a  terene  compound  as  they  did  not  investigate  its  con- 
stitution. 

Michael5  next  showed  that  the  compound  described  by  these  investi- 
gators is  i-phenyl-2,3-naphthalenedicarboxylic  anhydride.  He  proved 
this  by  preparing  a  specimen  by  Lanser's  method  and  finding  it  identical 
in  every  respect  with  a  specimen  prepared  by  the  method  of  Michael 
and  Bucher. 

Recently,  Stobbe*  obtained  this  anhydride  by  the  action  of  light  on 
dibenzalsuccinic  anhydride.  Failing  to  get  diphenyltetracarboxylic 
acid  by  direct  oxidation  but  obtaining  ortho-benzoylbenzoic  acid,  he 
claimed  to  have  shown  the  truth  of  the  naphthalene  formula  of  Michael 
and  Bucher  for  the  first  time. 

These  investigators7  showed  that  his  failure  to  get  the  diphenyltetra- 
carboxylic acid  was  due  to  incomplete  oxidation8  and  that  they  had 

1  Ber.,  32,  2478  (1899). 

2  Ibid.,  33,  3083  (1900). 
1  Ibid.,  35,  1407  (1902). 

4  J.  Ckem.  Soc.,  87,  1389  (1905). 

8  Ber.,  39,  1908  (1906). 

•  Ibid.,  40,  3372  (1907). 

7  Ibid.,  41,  70  (1908). 

1  Tins  JOURNAL,  30,  1246  (1908). 

25 


215 


ACIDS   OF  THE   PHENYIvPROPIOLIC   SERIES. 


noticed  the  formation  of  ortho-benzoylbenzoic  acid  by  the  direct  oxida- 
tion1 of  the  anhydride  as  well  as  from  the  hydrocarbon. 

Pfeiffer  and  Moller2  have  polymerized  phenylpropiolic  ester  to  the 
ester  of  i-phenyl-2,3-naphthalenedicarboxylic  acid  by  simply  heating 
to  200°.  They  point  out  that  aromatic  acetylene  derivatives  may  thus 
be  polymerized  to  naphthalene  derivatives  without  the  use  of  condensing 
agents.  The  earlier  work  of  Lanser  also  shows  this  since  Michael  has 
shown  that  the  so-called  triphenyltrimesic  acid  is  really  a  naphthalene 
derivative.  Lanser  obtained  the  anhydride  of  this  acid  by  heating 
phenylpropiolic  acid  to  a  temperature  above  200°.  Pfeiffer  and  Holler's 
work,  however,  illustrates  the  additional  fact  that  anhydride  formation  is 
not  essential  for  this  naphthalene  condensation. 

I  have  confirmed  Lanser's  experiment  and  have  been  able  to  get  a 
much  better  yield  of  the  ester  of  the  naphthalene  acid  than  Pfeiffer  and 
Moller  got.  In  my  experiment,  however,  the  phenylpropiolic  ester  was 
polymerized  by  heating  it  with  acetic  anhydride  instead  of  heating  it 
alone. 

These  investigations  show  that  phenyl  propiolic  acid  and  its  ester  or 
chloride  can  be  polymerized  in  a  number  of  different  ways  to  naphthalene 
derivatives  but  that  the  original  method  of  Michael  and  Bucher  which 
gives  a  quantitative  yield  is  still  the  best.  The  following  formulas  in- 
dicate how  this  change  takes  place : 


C.COjH 


CH 


This  work  has  been  continued  in  this  laboratory  for  a  number  of  years 
in  order  to  determine  whether  this  transformation  is  general  or  not. 
Besides  phenylpropiolic  acid,  eleven  of  its  substitution  products 
have  been  examined  thus  far  and  in  every  case  they  polymerized,  on 
heating  with  acetic  anhydride,  to  derivatives  of  i-phenyl-2,3-naph- 
thalenedicarboxylic  anhydride.  The  facts  thus  far  obtained  justify  the 
statement3  that  phenylpropiolic  acid  and  its  substitution  products  show  a 
strong  tendency  to  polymerize,  with  the  wandering  of  an  ortho  hydrogen  atom, 
to  phenylnaphthalene  derivatives. 

1  Am.  Chem.  J.,  20,  112  (1898). 

»  Bar.,  40,  3839  (1907). 

•THIS  JOURNAL,  30,  1262  (1908). 

26 


ORGANIC  AND   BIOLOGICAL.  2l6 

In  fact,  this  kind  of  polymerization  is  the  only  form  which  has  been 
thus  far  obtained  from  aromatic  propiolic  acids. 

In  this  work  much  time  was  spent  in  preparing  the  aromatic  propiolic 
acids  as  it  was  usually  necessary  to  either  prepare  new  compounds  or 
else  to  improve  the  methods  of  preparation  of  acids  which  were  already 
known.  In  most  cases  methods  were  found  by  which  these  interesting 
acids  could  be  prepared  readily  from  comparatively  inexpensive  materials 
— providing  that  suitable  precautions  were  observed. 

Phenylpropiolic  acid  was  prepared  in  the  usual  way  from  cinnamic 
acid  by  making  cinnamic  ester  dibromide.  It  is  well  known  that  alco- 
holic potash  converts  this  into  a  mixture  of  the  salts  of  allo-bromocinnamic 
acid  and  bromocinnamic  acid  and  that  the  latter  is  easily  converted  into 
phenylpropiolic  acid  by  the  loss  of  hydrobromic  acid.  The  former  acid 
is  so  stable,  however,  that  it  is  not  practicable  to  convert  it  into  phenyl- 
propiolic acid  directly  by  further  heating  with  alcoholic  potash.  It  can, 
however,  be  converted  into  the  isomeric  acid  by  simply  heating  it.  This 
acid  can  then  be  converted,  in  turn,  into  phenylpropiolic  acid.  This 
change  of  the  labile  bromo  acids  into  the  corresponding  isomeric  acids 
was  found  to  be  quantitative  in  several  cases.  In  the  case  of  the  allo- 
bromocinnamic  acid  it  was  noticed  that  when  it  was  heated  with  acetic 
anhydride  to  100°  its  own  anhydride  was  produced  but  at  a  higher  tem- 
perature this  was  transformed  into  the  bromocinnamic  anhydride.  The 
latter  could  then  be  transformed  into  phenylpropiolic  acid.  From  this, 
it  is  evident  that  it  is  not  necessary  to  use  pure  phenylpropiolic  acid 
in  this  work.  It  generally  seemed  desirable,  however,  to  separate  the 
acids  first.  A  very  good  way  of  doing  this  is  to  crystallize  them  from 
carbon  disulphide  or  from  carbon  tetrachloride.  In  this  way  it  is  possible 
to  separate  much  of  the  phenylpropiolic  acid  from  the  more  soluble  allo- 
bromocinnamic  acid. 

In  some  other  cases,  the  potassium  salts  of  the  propiolic  acids  were 
found  to  be  very  sparingly  soluble  in  the  alcoholic  potash,  thus  yielding 
the  pure  acids  at  once.  In  all  cases  the  potassium  salts  of  the  labile 
bromocinnamic  acids  were  found  quite  soluble  while  the  ammonium  salts 
of  the  isomeric  acids  were  very  sparingly  soluble.  These  properties  were 
found  very  useful  in  separating  the  resulting  phenylpropiolic  acids  from 
these  labile  substituted  bromocinnamic  acids  which  were  formed. 

The  meta-  and  para-nitrophenylpropiolic  acids  can  be  prepared  from 
the  corresponding  nitrobenzoic  aldehydes  by  Perkin's  synthesis.  In 
some  other  cases  Claissen's  synthesis  was  found  preferable  to  that  of  Per- 
kin. 

It  was  also  found  that  the  ortho-  and  para-nitrophenylpropiolic  acids 
could  be  converted  into  the  corresponding  halogen  acids  by  means  of  the 
diazo  reaction. 

Besides  phenylpropiolic  acid,  the  following  substitution  products  were 
prepared :  Piperonylpropiolic  acid,  o-chloro-,  o-bromo-,  w-nitro-,  m-chloro-, 
p-nitro-,  p-chloro-,  p-bromo-,  p-iodo-,  />-methoxy-,  and  ^-methylphenyl- 
propiolic  acids.  These  all  polymerize  readily  to  derivatives  of  i-phenyl-2,3- 
naphthalenedicarboxylic  anhydride  when  they  are  heated  with  acetic 
anhydride.  In  the  earlier  work  it  was  found  very  difficult  to  prove  this 
constitution  for  these  products.  The  method  used  in  case  of  the  first 
compound  has  already  been  described.  The  meta-  and  para-nitro 
compounds  were  oxidized  and  then  converted  into  diphenyltetracar- 

27 


217 


ACIDS   OF  THE   PHENYLPROPIOLIC  SERIES. 


boxylic  acid  thus  showing  them  to  be  naphthalene  derivatives.  By 
means  of  the  diazo  reaction,  they  were  then  converted  into  the  halogen 
derivatives  identical  with  those  obtained  by  direct  polymerization.  This 
showed  the  latter  to  have  the  same  constitution.  The  constitution  of 
the  product  from  the  para-methylphenylpropiolic  acid  was  established 
by  oxidizing  it  to  a  diphenylpentacarboxylic  acid.  In  more  recent 
work  the  very  efficient  method  of  oxidizing  to  benzenepentacarboxylic 
acid  described  below  was  used.  By  means  of  this  method,  which  depends 
on  the  catalytic  action  of  manganese  nitrate  in  fuming  nitric  acid,  eleven 
of  these  acids  were  oxidized  to  benzenepentacarboxylic  acids,  thus  con- 
firming the  naphthalene  constitution  which  had  previously  been  assigned 
for  some  of  the  substances. 

The  following  description  gives  an  idea  of  some  of  the  transformations 
which  these  substances  undergo:  They  are  all  ortho-dibasic  acids  from 
which  water  splits  out  easily  on  heating.  In  fact,  the  first  acid  obtained 
is  partially  converted  into  its  anhydride  even  on  crystallizing  it  from  only 
moderately  heated  glacial  acetic  acid.  In  this  way,  I  obtained  eight 
grams  of  the  anhydride  from  twenty  grams  of  the  acid.  This  loss  of 
water  in  crystallizing  the  acid  from  hot  solvents  led  to  the  statement, 
made  in  the  first  description,  that  the  acid  passed  into  the  anhydride 
spontaneously.  This  statement  was  corrected  in  a  later  paper  by  Michael. 
All  of  these  acids  have  this  general  property  and  some  of  them,  as  well  as 
their  oxidation  products,  may  show  properties  similar  to  those  noticed 
by  Orndorff  in  the  case  of  tetrachlorophthalic  acid. 

The  acids  all  necessarily  contain  a  carboxyl  group  with  both  ortho 
positions  substituted.  According  to  V.  Meyer's  observations  one  might 
expect  difficulty  in  esterifying  these  acids.  This  was  found  to  be  the 
case,  little  or  no  neutral  ester  being  found,  on  heating  the  substances  with 
alcohol  and  sulphuric  acid  under  the  usual  conditions.  If  more  sulphuric 
acid  is  used  and  the  heating  continued  for  a  longer  time  from  40  to  60 
per  cent,  of  neutral  ester  may  be  obtained. 

Sulphuric  acid  converts  the  i-phenyl-2,3-naphthalenedicarboxylic 
acid  into  red  allo-chrysoketonecarboxylic  acid. 


H 


CH 


.COjH 
.CO.H 


.00,11 


H 


JCH 


CH  CH 

I.  II. 

When  this  red  acid  is  heated  to  218°  with  potassium  hydroxide,  it  is 

28 


ORGANIC  AND   BIOLOGICAL. 


218 


changed   practically   quantitatively  into  a  new    i-phenylnaphthalenedi- 
carboxylic  acid. 

CH          CH 
C 


Formulas  I,  II  and  III  show  a  method  of  transferring  a  carboxyl 
group  from  the  ortho  position  on  one  ring  to  the  corresponding  position 
on  the  other  ring.  When  the  new  acid  (III)  is  heated  with  sulphuric  acid, 
a  new  red  acid  different  from  the  allochrysoketonecarboxylic  acid  (II)  is 
obtained. 

The  oxidation  of  these  naphthalene  acids  in  alkaline  potassium  per- 
manganate solution  has  already  been  described.  The  yield  of  diphenyl- 
tetracarboxylic  acid  is  usually  small,  since  the  intermediate  ketonic  acids 
are  very  stable  towards  alkaline  potassium  permanganate. 

HO,C.O~ 
/    \ 
HOC 


H02C.C 


These  ketonic  acids  are  very  easily  oxidized  to  diphenyltetracarboxylic 
acids  when  the  solution  is  acidified.  Formulae  I,  IV,  V  and  VIII 
indicate  these  reactions.  These  acids  are  obtained  in  the  form  of  sirup- 
like  solutions  and  they  resemble  phthalonic  acid  closely.  Heated  with 
caustic  alkalies,  they  yield  diphenyltricarboxylic  acids  and  oxalic  acid. 


29 


219 


ACIDS  OF  THE   PHENYLPROPIOUC   SERIES. 


On  reduction  with  hydriodic  acid,  the  weto-glyoxylic  acid  (V)  first  yields 
methyldiphenyltricarboxylic  acid  (VI)  which  then  reduces  at  a  higher 
temperature  to  a  methylfluorenecarboxylic  acid.  The  isomeric  ortho- 
glyoxylic  acid  (IV),  aven  at  the  boiling  point  of  hydriodic  acid,  reduces 
to  a  fluorenetricarboxylic  acid  (VII). 

CH  CH 


H8C. 


HO2C. 


HO2C. 


C.CO2H 


C.CO,H 


VII. 

This  shows  the  ease  with  which  diphenylcarboxylic  acids  close  the  ring 
to  form  fluorene  derivatives.  The  same  tendency  is  shown  by  the  action 
of  sulphuric  acid  on  diphenyltetracarboxylic  acid  (VIII)  in  forming  the 
yellow  diphenyleneketonetricarboxylic  acid  (IX),  which  can  be  reduced 
to  the  acid  represented  by  formula  VII.  I  have  found  this  closing  of  the 
ring  on  heating  to  100°  with  sulphuric  acid,  to  take  place  when  all  the 
carboxyl  groups  were  on  the  same  ring  but  generally  not  when  the  car- 
boxyl  groups  were  on  different  rings.  In  diphenyleneketonecarboxylic 
acids  of  the  general  form  IX,  the  ring  is  broken  in  such  a  way,  on  heating 
with  potassium  hydroxide,  that  the  carboxyl  group  is  transferred  from 
the  ortho  position  on  one  ring  to  the  corresponding  ortho  position  on  the 
other.1  In  this  case,  about  299  parts  out  of  300  are  changed  in  this  way — 
making  the  process  practically  quantitative.  The  following  formulas 
show  these  changes. 

The  very  sharp  breaking  of  the  ring  at  a  in  formula  IX  and  in  the 
similar  case  of  the  red  acid  (II)  indicates  a  tendency  to  remove  the 
carboxyl  groups  as  far  as  possible  from  each  other  and  suggests  the  pos- 
sibility of  its  giving  a  means  of  testing  the  constitution  of  the  resulting 
acid.  For  example  Bamberger  and  Hooker,3  after  heating  a  yellow 
diphenyleneketonedicarboxylic  acid  from  retene  with  caustic  alkali, 
represent  the  resulting  white  diphenylenetricarboxylic  acid  as  having 
the  three  carboxyl  groups  on  the  same  ring.  This  seemed  scarcely  pos- 
sible in  view  of  the  above  facts  and  an  examination  showed  the  acid  to 
have  a  different  structure. 

The  yellow  diphenyleneketonetricarboxylic  acid  (IX)  also  furnishes 
a  means  of  oxidizing  these  i-phenyl-2,3-naphthalenedicarboxylic  acids 
or  diphenylpolycarboxylic  acids  (like  I  and  VIII)  to  benzenepentacar- 

1  THIS  JOURNAL,  30,  1261  (1908). 
1  Ann.,  229,  159  (1885). 


ORGANIC   AND   BIOLOGICAL. 


22O 


CH 


,C.CO2H 

ic.co2H 


C.CO3H 
XI. 


boxylic  acids.  The  latter  acid  (VIII)  is  very  stable  towards  alkaline  potas- 
sium permanganate  as  on  heating  for  six  weeks  I  recovered  28  per  cent, 
of  unchanged  acid  and  could  not  isolate  any  benzenepentacarboxylic  acid. 
The  yellow  acid  (IX),  however,  decolorized  the  theoretical  quantity  of 
permanganate  in  less  than  two  hours.  The  very  soluble  acid  product 
was  not  completely  oxidized  but  it  yielded  benzene  for  the  hydrocarbon. 
Many  experiments  were  made  in  attempting  to  complete  the  reaction 
but  without  success.  Even  heating  on  the  water  bath  with  fuming  nitric 
acid  did  not  aid  very  much.  A  small  quantity  of  manganese  nitrate 
was  then  added  to  the  hot  nitric  acid.  Brisk  effervescence  began  at  once 
and  in  a  few  moments  pure  benzenepentacarboxylic  acid  separated  front 
the  liquid.  The  yield  in  this  experiment  was  about  90  per  cent,  of  the 
theory.  The  manganese  nitrate  is  evidently  a  very  efficient  catalytic 
agent  in  this  case.  This  method  was  also  applied  to  the  acids  without 
first  converting  them  into  ketone  derivatives,  and,  in  eleven  cases  out  of 
the  twelve  tested,  benzenepentacarboxylic  acid  was  found.  Not  only 
does  this  give  a  very  powerful  method  for  determining  constitution  but 


221  CATALYSIS  ON  THE   BASIS  OF  WORK   WITH   IMIDO   ESTERS. 

it  gives  a  very  easy  method  of  preparing  the  hitherto  almost  inaccessible 
benzenepentacarboxylic  acid.  It  also  serves  for  the  preparation  of 
other  benzene  polycarboxylic  acids.  Bamberger  and  Hooker's  diphenyl- 
eneketonedicarboxylic  acid  from  retene  can  be  oxidized  in  a  few  hours 
to  two  isomeric  benzenetricarboxylic  acids,  thus  showing  that  the  constitu- 
tion given  for  retene  and  all  its  derivatives  is  incorrect. 

The  above  work  dealing  with  the  action  of  acetic  anhydride  led  to  the 
supposition  that  anhydrides1  might  be  prepared  from  meta-  and  para- 
phthalic  acids  and  their  substitution  products.  On  trying  the  experi- 
ment it  was  found  that  such  anhydrides  could  be  obtained  quantitatively 
by  heating  a  solution  of  the  acid  in  acetic  anhydride  to  200°  until  the 
excess  of  reagent  was  distilled  off.  These  products  apparently  have  a 
very  high  molecular  weight.  A  preliminary  determination,  in  nitro- 
benzene by  the  boiling  point  method,  for  the  anhydride  from  chlorotere- 
phthalic  acid,  [C6HBCl(CO)2O]x,  indicates  that  it  may  be  as  high  as  1500 
or  2000. 

A  part  of  this  work  has  been  carried  on  with  the  aid  of  my  students 
and  I  wish  especially  to  acknowledge  the  valuable  assistance  of  G.  F. 
Parmenter,  N.  A.  Dubois,  V.  S.  Babasinian,  M.  L.  Dolt,  W.  C.  Slade 
and  F.  Keyes. 

The  more  important  results  of  this  work  thus  far  are  as  follows : 

1.  Satisfactory  methods  for  the  preparation  of  a  number  of  aromatic 
propiolic  acids. 

2.  The  polymerization  of  these  acids  to  derivatives  of  i-phenyl-2,3- 
naphthalenedicarboxylic   acids — giving   a   quantitative   method   of   syn- 
thesis. 

3.  Syntheses  of  acids  of  the  diphenyl,  fluorene  and  diphenyleneketone 
series  and  a  study  of  their  characteristic  reactions. 

4.  Syntheses    of    benzenepentacarboxylic    acid    and    other    benzene- 
polycarboxylic  acids. 

5.  The  determination  of  the  constitution  of  retene  and  its  derivatives. 

6.  The  preparation  of  anhydrides  from  meta-  and  para-phthalic  acids 
and  their  substitution  products. 

BROWN  UNIVERSITY,  PROVIDENCE,  R.  I. 


CATALYSIS  ON  THE  BASIS  OF  WORK  WITH  IMIDO  ESTERS.2 

BY  JULIUS  STIEGLITZ. 
Received  December  2,  1909. 

I  shall  not  attempt  to  discuss  to-day  the  general  subject  of  catalysis 
but  shall  use  the  short  time  rather  to  present  briefly  some  results3  in 
certain  lines  of  our  work  which  seem  to  shed  some  light  on  three  funda- 
mental points  of  interest  in  catalysis,  namely,  on  the  questions  how  in 

1  THIS  JOURNAL,  30,  1263  (1908)  and  31,  1319  (1909). 

1  Presented  at  the  Second  Decennial  Celebration  of  Clark  University,  Worcester, 
Mass.,  September  15,  1909. 

'  Certain  parts  of  the  work  are  still  being  carried  out — as  indicated  below — and 
for  such  parts  this  report  is  preliminary  to  a  final  one.  Complete  discussion  of  the 
several  parts  lay  outside  the  limits  of  this  paper  and  will  be  brought  in  in  later  special 
reports. 

32 


ORGANIC   AND    BIOLOGICAL.  222 

certain  cases  a  catalytic  agent  does  its  work,  why  it  does  it,  and  what 
limitations  there  are  to  its  action. 

It  may  be  recalled  that  an  imido  ester,  such  as  methyl  imido  benzoate, 
is  very  slowly  decomposed  by  pure  water.  One  of  the  decompositions 
it  undergoes  under  these  conditions  is  into  ammonia  and  methyl  benzoate1 
as  expressed  in  the  equation 

C6H5C(  :  NH)OCH3  +  H2O  — >  C6H6CO2CH3  +  NH3.      (i) 
The  addition  of  an  acid,  say  hydrochloric  acid,  enormously  accelerates 
this  otherwise  extremely  slow  action  and  we  were  able  to  show  that  the 
acceleration  is  due  to  the  fact  that  the  reacting  component  in  this  decom- 
position is  the  positive  ion  of  the  ester,2  as  expressed  in  the  equation. 

CflH5(  :  NH2+)OCH3  +  H2O  — ^  C6H5CO2CH3  +  NH4+.  (2) 
In  arriving  at  this  conclusion,  account  had  to  be  taken  of  the  so-called 
"salt-effect"  or  "salt-acceleration"  produced  by  the  presence  of  elec- 
trolytes, entirely  analogous  to  the  "salt-effect"  in  other  decompositions 
in  which  water  is  a  reacting  component,  as  in  the  catalysis  of  esters  by 
acids.  This  salt-effect  being  allowed  for,  the  velocity  of  decomposition 
of  an  imido  ester  by  water  in  the  presence  of  acids  is  given  in  the  equation3 

dxfdi  =  Kv(ion}  X  C^  M/.  *„  X  [CH  X  COH}.  (3) 

I  have  not  time  more  than  to  mention  the  fact  that  it  was  shown  that 
the  same  fundamental  equation  may  be  applied  to  the  saponification  of 
ordinary  esters  under  the  influence  of  acids,  the  main  difference  being 
that  for  such  exceedingly  weak  oxonium  bases  as  esters  are  the  con- 
centration of  the  positive  ester  ion  is  practically  proportional  to  the 
concentrations  of  the  ester  and  the  hydrogen  ion  present  at  any  moment, 
so  that  we  may  transform  (3)  into4 

dx/dt  =  KVX  Cester  XCHX  [CH  X  COH]  (4) 

which  is  also  the  equation  based  on  experience. 

The  work  on  which  the  above  conclusions  were  based  was  carried 
out  wholly  with  the  hydrochlorides  of  the  imido  esters.  More  recently 
we  have  also  carried  out  measurements  with  the  hydrobromides  and 
nitrates,  and  begun  work  also  with  sulphates;  if  the  positive  ion  is  the 
reacting  component,  then,  determining  rigorously  the  degree  of  ionization 
and  making  rigorous  allowance  for  the  salt-effect,  we  should  find  that  the 
velocity  constant  for  the  decomposition  of  the  positive  ion  in  the  chloride 
solution  should  also  satisfy  the  observed  rates  of  decomposition  of  these 
other  salts.  For  the  rigorous  treatment,  the  "salt-effect"  produced  by 
the  chlorides,  bromides,  nitrates,  etc.,  has  to  be  determined  experimen- 
tally and  this  has  been  carried  out5  with  the  chlorides  and  bromides,6 
mixtures  with  varying  amounts  of  the  potassium  and  sodium  salts  being 
examined,  the  degrees  of  ionization  of  each  salt  in  the  mixture  being 
1  Stieglitz,  Report  International  Congress  of  Arts  and  Science,  St.  Louis,  4,  276 
(1904),  and  Am.  Chem.  J.,  39,  29  (1908). 

*  Stieglitz  with  Derby,  McCracken,  Schlesinger,  Am.  Chem.  J.,  39,  29,  166,  402, 
437,  586,  719. 

3  Cpos.  est.  ion  1S  a  function  of  x. 

*  Cgster  is  a  function  of  x. 

'  W.  W.  Hickman,  Dissertation,  1909. 

'  Mr.  Weatherby  is  completing  the  work  begun  by  Mr.  Hickman  on  the  nitrates 
and  sulphates. 

33 


223  CATALYSIS   ON  THE   BASIS   OF  WORK  WITH   IMIDO   ESTERS. 

determined  with  the  aid  of  the  principle  of  isohydric  solutions,  which 
was  proved  to  apply  to  such  mixtures.1  The  salt-effect  is,  except  for 
minute  quantities  of  salt,  proportional  to  its  concentration  or  rather, 
more  probably,  only  to  the  concentration  of  the  ionized  part  of  the  salt.. 
The  salt-effect  is  an  acceleration  and  if  we  call  KV(ion)0  the  velocity  of 
decomposition  of  the  imido  ester  ion  in  the  absence  of  any  salt  at  all, 
this  velocity  will  be  increased  proportionally  to  some  specific  acceleration 
factor  A,  and  to  the  concentration  ma  of  the  ionized  part  of  A  salt.  So  we 
have 

K,(M)ob,.  =  K,<io«)o  (1  +Ama).  (5) 

Kv(ion)obs.  is  the  constant  calculated  according  to  equation  (3)  from 
the  observations  without  any  allowance  for  a  salt-effect. 

Kv(ion)o,  the  velocity  constant  when  the  salt  effect  is  eliminated,  is  easily 
found  by  extrapolation  from  the  observations  when  imido  ester  salts 
are  present  without  added  salts,  A  from  the  results  obtained  when  salts 
have  been  added.  We  arrived  thus  empirically  at  the  rather  unexpected 
result  that  the  accelerating  factor  A  is  approximately  the  same  for 
sodium,  potassium  and  lithium  chlorides  and  for  the  bromides  as  well 
as  for  the  chlorides,  viz.,  about  185  per  cent,  per  gram  molecule  of  fully 
ionized  salt.  Table  I  illustrates  this  fact  for  potassium  chloride  and 
potassium  bromide.  Kv  is  the  velocity  coefficient  calculated  without 
regard  to  the  degree  of  ionization  of  the  imido  ester  salt,  a  is  the  degree 
of  ionization  of  the  salt  calculated  with  the  aid  of  the  principle  of  iso- 
hydric solutions.  In  the  columns  headed  "found"  are  given  the  values 
obtained  for  Kv\a  by  experiment;  in  the  columns  headed  "calculated" 
are  the  values  obtained  according  to  equation  (5),  in  which  the  velocity 
coefficient  Kv(ion)0  in  the  absence  of  any  salts  at  all  is  taken  as  164  and  the 
salt  acceleration  factor  A  is  taken  as  185  per  cent,  for  both  series. 

TABUJ  I.1 

KCl.  KBr. 

43430  K-oja.  43430/S^/a. 


K  Hal. 


m.  Found.  Calculated.  Found.  Calculated, 

o  176  176  176  177 

O.I  191  190  191  190 

0.2  213  214  209  215 

0.25  227  226  230  227 

0.333  247  245  (268)  247 

I  wish  to  emphasize  this  result  because  the  work  of  others,  notably  of 
Arrhenius  and  Euler,  with  cane-sugar  and  esters,  shows  varying  specific 
accelerating  factors  for  these  salts.  I  believe  our  work  has  the  advantage 
of  our  knowing  from  conductivity  measurements  the  degrees  of  ioniza- 
tion of  the  imido  ester  salts  as  well  as  of  the  added  electrolyte  so  that 
there  seems  to  be  no  unknown  factor  left  in  our  estimations.  But  we  are 
simply  presenting  these  results  for  the  time  being  as  an  empirical  contri- 
bution to  the  whole  question  of  catalysis  and  we  do  not  consider  the 
very  complex  question  of  "salt  catalysis"  as  at  all  settled.3 

.  *  Edith  E.  Barnard,  Dissertation,  1907. 
3  Taken  from  W.  W.  Hickman's  dissertation. 

3  Work  on  "salt  catalysis"  is  being  continued  by  L.  S.  Weatherby,  preliminary 
results  by  Mr.  Hickman  on  the  effect  of  sulphates  indicated  an  abnormally  high  effect. 

34 


ORGANIC  AND   BIOLOGICAL.  224 

With  the  aid  of  the  determination  of  the  salt  factor  for  chlorides  and 
bromides  we  have  been  able  to  show  that  the  positive  ester  ion  shows 
indeed  the  same  rate  of  decomposition  irrespective  of  its  origin  from  either 
of  these  salts  and  very  probably  also  for  the  nitrate1  (see  the  values  for 
Kvia  for  the  three  salts  in  equi-molar  concentrations  as  given  in  Table  II). 
This  is  exactly  what  our  theory  would  require,  namely,  that  the  simple 
reason  why  the  addition  of  an  acid  accelerates  this  decomposition  is  that 
it  forms  a  salt  whose  positive  ion  is  the  reacting  component  and  that  the 
concentration  of  the  ion  is  enormously  increased  when  the  catalyzing 
acid  is  added  to  the  free  ester,  which  is  a  very  weak  and  therefore  little 
ionized  base.  . 

TABLE  II.* — ETHYL  IMIDO  BENZOATE. 

Hydrochloride.  Hydrobromide.  Nitrate. 

^».  0.8        Kv.*  JftjT  «•*       Kv*    Kfa.  o.«       Kv*   Kvla. 

0.05  77.8  136  175  75-9  133  i?6  75-1   133  177 

o.i   71.8  132  185  69.4  128  184          68.3  127  186 

0.2   64.5  121   188          61.7  119  193          60.4  118  195 

0-33  57-7  "4  198  54-7  108  198          52.7  107  201 

It  was  suggested  by  Arrhenius  and  emphasized  by  Euler  that  the 

salt  acceleration  is  probably  largely  due  to  the  increased  ionization  of 

water  in  the  presence  of  electrolytes,  but  quantitative  evidence  in  support 

of  such  a  conclusion  has  not  been  brought,  as  far  as  I  am  aware.     In  view 

of  the  increase  observed  by  Arrhenius  arid  others5  in  the  strength  of  other 

acids  in  the  presence  of  added  foreign  salts,  e.  g.,  of  acetic,  formic  and 

carbonic  acids  in  the  presence  of  sodium  chloride,  it  seems  a  sufficiently 

rational  assumption  that  water  should  show  a  similar  increased  ionization.6 

The  imido  esters,  enabling  us  to  measure  the  actual  concentration  of  the 

reacting  imido  ester  ion,  gave  us  an  opportunity  to  bring  experimental 

evidence  strongly  supporting  this  view.     From  equation  (3)  it  is  obvious 

that  if  the  salt  acceleration  is  due  to  the  increased  ionization  of  water, 

viz.,  an  increase  in  the  value  of  the  third  factor,  (CH  X  COM)  then,  Cpos.  M<.  ion 

being  known   by   experiment,  the  velocity   constant  Kv(ion)    calculated 

-without  taking  any  increased  value  of  [C#  X  COH]  into  account,  should 

increase  in  the  same  proportion  for  all  the  imido  esters  for  the  same 

concentration  of  added  salt  ions,  irrespective  of  the  fact  that,  according 

to  the  ester  used,  the  decomposition  may  be  a  comparatively  slow  or  a 

very  fast  one.     We  have  found  this  to  be  true7 — all  the  esters  used  show 

the  same  acceleration  per  gram  molecule  ionized  salt — i.   e.,  close  to 

185  per  cent,  per  gram  molecule  ionized  potassium  chloride,  etc.8 

Having  found  that  the  reacting  component  in  these  and  a  number 
of  other  actions  under  the  influence  of  acids  is  the  positive  ion  of  a  salt 
formed  with  the  acid,  we  were  naturally  most  interested  in  the  question 

1  The  salt  effect  for  nitrates  is  now  being  determined. 
1  Taken  from  W.  W.  Hickman's  dissertation. 

3  Taken  from  Edith  E.  Barnard's  dissertation. 

4  Taken  from  Schlesinger's  results,  Loc.  cit. 

*  E.  J.  Szyszkowski,  Z.  physik.  Chem.,  58,  419. 

•  See  a  discussion  of  the  other  side  of  this  question  by  Acree,  Am.  Chem.  J.,  41, 474- 

7  Dissertation  of  Edith  E.  Barnard  and  W.  W.  Hickman. 

8  The  investigation  of  the  ionization  of  water  in  salt  solutions  is  being  continued 
with  other  substances  and  by  other  methods. 

35 


225  CATALYSIS  ON  THE   BASIS   OF   WORK  WITH   IMIDO   ESTERS. 

why  the  ion  should  be  so  reactive,  why  it  should  be  so  important  a  com- 
ponent. We  can  hardly  consider  the  decompositions  to  be  purely  ionic 
reactions,1  comparable  with  the  hydrolysis  of  salts  in  aqueous  solutions, 
as  was  mistakenly  assumed,  for  instance,  by  Euler  and  by  Kastle.  Such 
assumptions  run  counter  to  the  law  of  mass  action  applied  rigorously  in 
the  analysis  of  the  conditions.1  The  law  is,  however,  in  agreement  with 
the  assumption2  based  on  experience  gained  in  organic  chemistry  that  the 
following  are  the  stages  for  the  action  : 


. 

C,HsCf  +H+  +  OH-—  *-C,H6C—  OIH  —  *-t^H5CO,CH,  +  NH,+    (6) 

\OCH, 

Now,  we  may  well  ask  why  this  should  be  an  enormously  faster  action 
than  the  entirely  analogous  possible  action  of  water  on  the  non-ionized 
free  ester,  which,  it  is  clear,  could  proceed  in  a  very  similar  series  of  stages 
as  expressed  in  the  equations  : 


C,H6C^          +H+  +  OH-— »C,HSC—  O:H  — *  C,H6CO,CHa+NH,,.     (6') 
\OCH.  \o£j- 

For  me,  one  of  the  most  interesting  and  important  features  of  our 
work  is  found  in  the  unmistakable  way  in  which  the  fact  is  brought  out 
more  and  more  clearly  that  the  accelerating  or  catalytic  effect  of  the 
acid  is  most  intimately  associated  with  the  transformation,  in  acid  solu- 
tion, of  the  positive  ion  of  a  weaker  base  into  that  of  a  stronger  one — 
the  results  no  doubt  of  the  principle  of  the  loss  of  a  maximum  amount 
of  free  energy.3  This  is  shown  most  strikingly  in  the  following  illustra- 
tion: whereas  the  above  imido  esters  are  very  rapidly  decomposed  by 
water  in  the  presence  of  acid,  this  is  not  the  case  for  the  closely  related 
compounds,  the  urea  ester  salts,  which,  structurally  considered,  could 
react  quite  as  easily  with  water  but  are  as  a  matter  of  fact  quite  stable 
in  acid  solution.  The  transformation 


/NH2+ 
NH2C<         '    +HOH—  >NH2C—  OH  -^  NH4++H2NCOOCH3       (7) 


only  takes  place  to  a  very  slight  extent  at  100°,  and  at  ordinary  tempera- 
tures, where  imido  ester  salts  are  completely  decomposed  in  one  to  ten 
hours,  the  urea  ester  salts  have  not  been  observed  to  decompose  at  all.4 
In  this  case  we  have  the  notable  fact  that  such  a  transformation  would 
involve  the  change  of  a  salt  of  a  stronger  base  into  that  of  a  much  weaker 
one  —  an  ammonium  salt  —  and  this  does  not  take  place.  To  test  the 
legitimacy  of  our  reasoning  we  recently  examined  the  behavior  of  ben- 
zoyl  urea  ester  salts:  the  benzoyl  urea  esters  form  very  much  weaker 

1  See  a  more  complete  discussion  by  Stieglitz,  Am.  Chem.  J  .,  39,  402. 

2  Stieglitz,  Loc.  cit. 
8  Ibid. 

*  The  degree  of  stability  is  being  examined  quantitatively. 

36 


ORGANIC   AND   BIOLOGICAL.  226 

bases  than  ammonia  and  our  reasoning  would  lead  us  to  expect  that  they, 
in  turn,  ought  to  be  decomposed  quite  as  smoothly  in  acid  solution  as  the 
imido  esters.  Such  is,  in  fact,  the  case;1  urethanes  and  ammonium  salts 
readily  result  according  to  the  equation 


C6H5CO.NH.Cf         +  HOH  —  >  NH4+  +  C6H5CONHCOOCH3.  (8) 
XOCH, 

We  find  then  that  perfect  analogy  in  structure  is  of  far  less  importance 
in  determining  the  result  of  the  action  of  water  than  a  definite  physico-chemical 
relation  subject  to  quantitative  measurement. 

This  is  again  brought  out  beautifully  by  the  behavior  of  the  urea  esters 
towards  ammonia.  The  imido  esters  give  with  ammonia  amidines  and 
again  the  action  is  accelerated  by  the  addition  of  an  acid  or  an  ammonium 
salt  and,  as  we  shall  see  presently,  this  is  due  to  the  fact  that  again  it  is 
the  positive  ester  ion  that  reacts  with  ammonia,  an  amidine  resulting 
according  to  the  equation 

C6H5C(  :  NH2+)OCH,  +  NH,  —  *•  CaH6C(  :  NH2+)NH2  +  HOCH3      (9). 

Now,  urea  esters  which,  as  explained  above,  would  not  react  with  water 
in  acid  solution  because  the  salt  of  a  stronger  base  would  be  converted 
into  the  salt  of  a  weaker  one  if  they  did  react,  would  give  with  ammonia 
guanidines  which  are  still  stronger  bases  than  they  are  themselves. 
They  should,  therefore,  according  to  this  theory,  react  with  ammonia  in 
the  presence  of  an  acid  ;  as  a  matter  of  fact  they  do,  producing  guanidines 
very  readily,  and  we  were  able  to  prove  again  that  the  velocity  of  the 
formation  is  proportional  to  the  concentration  of  the  positive  ester  ion;2 
in  fact,  until  our  theory  led  us  to  recognize  the  importance  of  having  a 
salt-forming  acid  present,  all  our  efforts  to  prepare  guanidines  from 
urea  esters  —  by  using  ammonia  alone  —  had  proved  futile;  so  that  this 
theory  seems  to  agree  equally  well  with  the  reactions  of  a  given  compound 
which  do  occur  as  with  those  which  do  not  take  place. 

We  have  found  too  that  in  series  of  structurally  closely  related  esters 
where  what  might  be  called  the  structural  and  stereochemical  resistances 
to  the  action  are  perhaps  approximately  the  same,  the  transformation 
of  the  positive  ion  of  a  weaker  base  in  the  presence  of  acids  into  that  of  a 
given  stronger  base,  say  into  the  ammonium  ion,  proceeds  with  the  greater 
velocity  at  a  given  temperature  the  weaker  the  original  base  is.3  This  brings, 
as  far  as  I  am  aware,  the  first  complete  experimental  proof  of  a  theory 
which  others,  notably  van't  Hoff  and  Euler  suspected  to  be  true,4  although 
there  appeared  so  many  marked  contradictions  to  the  assumption  that 
the  theory  appeared  at  best  a  very  uncertain  one.  For  instance,  Hemp- 
tinne5  and  Lowenherz,6  working  on  this  problem  at  van't  Hoff's  sug- 
gestion, obtained  the  following  results  for  the  saponification  of  esters  by 
acids  : 

1  J.  C.  Moore's  dissertation,  1909. 

1  R.  A.  Hall's  dissertation  (1907). 

»  Cf.  Stieglitz,  Loc.  cit.,  and  McCracken,  Loc.  cit. 

4  See  the  discussion  by  Euler,  Z.  physik.  Chem.,  36,  410. 

8  Ibid.,  13,  561. 

•  Ibid.,  15,  395. 

37 


227  CATALYSIS  ON  THE   BASIS  OF  WORK  WITH  IMIDO   ESTERS. 

TABLE  III.1 

Ester.                                                        Velocity  constant.  loniz.  const,  of  the  acid. 

HCOOC2H5 O.H  21        X   10- 

CH3COOC7H5 0.0057  i. 8X10- 

C1CH2COOC2HS 0.0033  155       X  io- 

C12CHCOOC2H5 0.0053  5ioo      X  io- 

CH3CH2COOC2H5 0.0061  i  .3  X  io~ 

Assuming,  as  Euler  did,  that  the  strongest  acids  produce  the  weakest 
bases  in  their  esters,  one  might  expect  the  positive  ions  of  the  chloroacetic 
acid  esters  to  be  saponified  most  rapidly  to  give  the  positive  ion  of  a 
given  stronger  base,  the  oxonium  base  of  ethyl  alcohol.  As  a  matter  of  fact 
the  velocity  constants  in  the  above  table  do  not  tell  us  anything  at  all 
as  to  whether  that  is  so  or  not  and  that  is  why  the  theory,  heretofore,  has 
appeared  as  an  unproved  one;  obviously  it  does  not  follow  from  the  data 
in  Table  III,  where  the  weakest  bases,  dichloroacetic  ester  and  chloroacetic 
ester,  have  the  smallest,  not  the  largest,  velocity  constants  of  decomposi- 
tion. But  the  fact  that,  for  instance,  the  velocity  coefficient  for  the 
saponification  of  dichloroacetic  ester  is  even  smaller  than  that  for  ethyl 
acetate  does  not  mean  anything  at  all  in  regard  to  the  real  relative  rates  of 
transformation  of  their  positive  ions:  there  is  a  second  factor  involved, 
namely,  the  concentrations  of  the  positive  ions  of  the  esters  are 
dependent  on  the  strength  of  the  esters  as  oxonium  bases,  as  expressed 
in  our  fundamental  equations  for  the  catalysis  of  an  ester  by  an  acid.2 
In  our  fundamental  equation 

dx/dt  =  Kv(ion)  X  C^  M,  ^  X  [CH  X  COH]  (io)3 

we  may  substitute  for  C^j.  est.  ion  the  relation  expressed  in : 

Cpos.  est.  ion  =  *«*/*'   X   CesU,  X   CH  (i  l)« 

and  have 

dx/dt  =  Kv(ion)  X  kaffjk'  X  Cester  X  CH  X  [CH  X  COH]      (12) 

=  Kv  X  Cester  X  CH  X  CH  X  COH  (13) 

which  is  the  ordinary  equation  representing  the  velocity  of  decomposition 
of  esters  by  acids.  What  we  determine  with  esters,  for  instance  in  Hemp- 
tinne's  and  Lowenherz's  work  as  expressed  in  Table  III  is  Kv  and  not 
the  more  fundamental  constant  KV(ion).  Now 

Kv  =  K,(M  X  hrfjk'  (14) 

and  it  is  obvious  that  if  the  basic  strength  of  the  ester  as  expressed  in 
kaff.  grows  very  much  smaller,  as  it  undoubtedly  does  when  we  go  from 
ethyl  acetate  to  ethyl  chloroacetate,  KV(ion)  could  easily  grow  very  much 
larger  and  yet  Kv  need  not  change  appreciably  or  it  might  even  grow  smaller, 
without  the  result  being  in  any  disagreement  whatever  with  the  theory 
expressed.  This  means,  of  course,  that  determinations  simply  of  the 
velocity  constants  Kv  of  decomposition  of  such  esters  do  not  prove  any- 

1  The  table  is  taken  from  Euler,  Loc.  tit.,  p.  412. 

2  Stieglitz,  International  Congress  of  Arts  and    Science,  St.   Louis,    1904,  4,   276 
of  the  report,  and  Am.  Chem.  J.,  39,  47  (1908). 

8  Cpos.  est.  ion  is  a  function  of  x. 

4  k'  is  the  stability  constant  of  the  oxonium  hydroxide.  kaftjk'  may  be  considered 
the  stability  constant  of  the  complex  ester  ion.  Cf.  Bredig,  Z.  Elektrochem.,  9,  118 
(foot-note). 

38 


ORGANIC   AND   BIOLOGICAL.  228 

thing  as  to  the  principle  at  issue.  A  somewhat  stronger  base  might 
well  give  a  higher  rate  of  change  than  a  weaker  one  by  virtue  of  the  fact 
that  a  larger  proportion  of  the  base  is  present  in  its  active  form,  the  ion, 
and  the  real  rate  of  decomposition  of  the  ion  may  be  much  smaller  than 
that  of  an  ester  giving  a  smaller  velocity  constant  Kv.  The  imido  esters 
have  the  advantage  that  their  affinity  constants  are  easily  ascertained 
and  we  do  not  deal  with  any  such  unknown  quantity  at  all,  and  thus  we  were 
able  to  bring  what  I  believe  is  the  first  experimental  proof  of  the  sound- 
ness of  the  theory.  An  apt  illustration  of  the  correctness  of  our  argu- 
ment concerning  the  lack  of  data  for  a  correct  analysis  of  results  like  those 
given  in  Table  III  is  found  in  the  following  facts:  the  formation  of  ami- 
dines  from  imido  esters,  as  was  stated,  is  greatly  accelerated  by  the  addition 
of  acids  or  of  an  ammonium  salt  and  we  were  able  to  show  that  the  amidine 
formation  may  be  considered  essentially  a  function  of  the  concentration 
of  the  positive  ester  ion,  proceeding  according  to 


C6H5C<  +  NH3—  >  C6H5C<  +  HOCH,  (9) 

X 


OCH3 
and 

dx/dt  =  KVX  Cpos_  est.  ^  X  CNHt 

Now,  if  we  develop  the  expression  for  the  concentration  of  the  positive 
ion  of  a  very  weak  base  like  an  imido  ester  in  the  presence  of  a  much 
stronger  one  like  ammonium  hydroxide  we  find  that: 


..  , 

*~NH3  Koff.  amm. 

and  by  substitution  we  get: 

fir  I  rlt  -  K  V  kaff-  est-       V  CesUr  X  CNH*+  V 

ax/at  -  Kv(ion)  X  ,  X 

Kaff.  amm. 

-       aft-  est-       / 


a/7.  amm. 

Now,  imido  ethyl  benzoate  forms  benzamidine  considerably  faster 
than  does  the  methyl  ester:  in  both  cases  the  change  is  from  the  salt  of 
the  positive  ion  of  a  weaker  base  to  that  of  a  much  stronger  one,  the 
amidine,  but  the  ethyl  ester  is  the  stronger  base  and  yet  it  reacts  the  faster 
and  apparently  contradicts  our  theory.  A  knowledge  of  the  affinity 
constants  shows,  however,  that  it  reacts  the  faster  only  because  by  virtue 
of  its  being  a  stronger  base  it  takes  a  larger  proportion  of  the  catalytic 
agent,  the  acid,  from  the  ammonium  chloride,  and  forms  a  proportionally 
larger  concentration  of  the  active  component,  the  ester  ion,  than  does 
the  methyl  ester  under  the  same  conditions.  Calculating  with  the  aid 

1  Cpos.  est.  ion  is  a  function  of  x. 

2  In  passing,  it  may  be  remarked  that  this  last  form  shows  that  the  action  may  be 
considered  one  of  the  ion  ammonium  acting  on  the  ester,  but  we  believe  our  original 
assumption  to  be  the  right  one  for  reasons  found  in  the  behavior  of  organic  compounds 
which  cannot  be  elaborated  here  ;  it  may  be  said,  for  instance,  that  we  have  found  NH, 
and  not  NH4+  to  react  with  ordinary  esters  to  form  amides  and  are  carrying  out  other 
more  crucial  experiments  on  this    point.       Vide    Acree,    Am.    Chem.    J.,    38,    308. 
Fitzgerald  and  Lapworth,  /.  Chem.  Soc.,  93,  2163. 

39 


229  CATALYSIS  ON  THE   BASIS  OF   WORK  WITH   IMIDO   ESTERS. 

of  the  affinity  constants  the  true  velocities  of  transformation  of  the  positive 
ions,  we  find  the  true  relation:  ^(ion)  for  the  methyl  ester  is  140/0.434 
and  for  the  ethyl  ester  only  69/0.434.  *  So  the  true  relations  resulting 
from  an  exact  knowledge  of  all  the  quantitative  constants  involved  agree 
perfectly  with  the  fundamental  principle  given. 

This  reaction  shows  other  points  of  great  interest:  for  instance,  the  fact 
that  the  concentration  of  ammonia  cancels  out  of  the  mathematical 
equation  leads  to  the  conclusion  that  the  velocity  of  decomposition  is 
independent  of  the  concentration  of  ammonia,  one  of  the  reacting  com- 
ponents. 

This  peculiar  conclusion  has  been  fully  verified  by  experience;  the 
velocity  constant  is  as  a  matter  of  experiment  almost,  although  not  ab- 
solutely, independent  of  the  concentration  of  ammonia ;  in  the  case  of  the 
above  methyl  ester,  the  constant  grows  only  about  10  per  cent,  with  an 
increase  of  400  per  cent,  in  the  concentration  of  the  ammonia.  This  ap- 
parent contradiction  with  the  law  of  mass  action  is  readily  understood 
if  we  remember  that  the  concentration  of  ammonia  has  two  effects  which 
oppose  each  other;  ammonia  does  accelerate  the  action  in  proportion  to 
its  mass  as  required  by  the  law,  but  it  also  to  the  same  degree  retards 
the  action  by  depriving  the  weaker  base  of  the  ionizing  and  therefore 
catalyzing  acid.  Within  a  year  Lapworth2  has  made  the  extremely 
important  discovery  that  water  stands  in  exactly  the  same  relation  to 
the  esters  in  the  catalysis  by  acids — only  then  the  two  bases  competing 
for  the  acid  are  two  oxonium  bases,  the  ester  and  water. 

And  now  in  conclusion  I  wish  to  call  attention  to  one  more  result  with 
these  imido  esters  which  has  impressed  us  very  much  and  which  seems 
to  me  to  throw  a  very  clear  light  on  the  whole  question  of  catalysis  or 
acceleration  by  showing  certain  limitations  to  catalytic  effects.  It  was 
mentioned  a  moment  ago  that  the  velocity  of  formation  of  benzamidine 
from  methyl  imido  benzoate  may  be  expressed  as  a  function  of  the  positive 
imido  ester  ion  and  that  it  is  almost  independent  of  the  concentration  of 
the  ammonia;  but  it  is  not  absolutely  independent,  there  is  a  slight  but 
steady  rise  in  the  value  of  the  constants  with  increasing  concentrations 
of  ammonia.  All  other  secondary  reactions  having  been  excluded  (e.  g., 
for  fourfold  increase  of  NH3,  the  constants  rise  gradually  from  139/0.434 
to  154/0.434)  as  the  cause  of  this  increase  by  a  knowledge  of  their  velocity 
constants,  we  suspected  that  besides  the  main  action  of  ammonia  on  the 
positive  ester  ion,  there  is  a  much  slower  action  of  ammonia  also  on  the 
non-ionized  free  ester,  namely,  that  we  have  two  simultaneous  actions: 
C8H6C(  :  NH2+)OCH,  +  NH,  — +•  CeH6C(' :  NH3+)NH2  +  HOCH,  (18) 

and 

C6H6C(  :  NH)OCH,  +  NHS  — >  C8H5C( :  NH)NH2  +  HOCH,  (19) 
We  had  the  more  reason  to  suspect  this  as  we  had  already  found  that 
water,  besides  decomposing  the  positive  ion  of  an  imido  ester  at  a  very 
high  speed,  also  undoubtedly  decomposes  the  non-ionized  ester  at  a  very 
slow  rate.8  It  was  found  that  the  experimental  results  agree  very  well 
with  this  conception  of  two  simultaneous  actions  in  the  formation  of 

1  Miss  Katharine  Blunt's  dissertation  (1907). 

2  Loc.  cit. 

*  In  this  case  the  products  are  different.     Vide  Stieglitz,  Derby  and  Schlesinger, 
Loc.  cit. 

40 


ORGANIC   AND   BIOLOGICAL.  230 

benzamidine  and  that  the  velocity  constant  for  the  action  of  ammonia 
on  the  positive  ester  methyl  ion  at  25°  is  325,  while  that  on  the  ester 
molecule  is  only  0.0069.  *  That  is,  the  positive  ion  is  almost  50,000  times 
as  reactive  as  the  non-ionized  molecule.  It  may  appear  somewhat 
surprising  that  such  a  small  constant  could  still  be  detected  side  by  side 
with  such  an  enormous  one,  the  whole  action  being  completed  in  one 
to  two  hours.  But  we  must  remember  that  for  the  ion  action  with  the 
enormously  high  rate  of  change  we  have  at  any  moment  only  minute 
quantities  of  the  reacting  component,  e.  g.,  0.000,005  gram  ion  at  the 
beginning  of  a  velocity  measurement,  which  is  used  up  at  an  enormous 
speed  but  always  formed  again  instantly  by  the  purely  ionic  action  of 
imido  ester  on  the  ammonium  chloride.  On  the  other  hand  the  transfor- 
mation of  the  non-ionized  molecule  has  the  advantage  of  relatively  high 
concentrations  of  each  of  the  reacting  components,  say  0.05  both  for  the 
ammonia  and  for  the  free  ester  at  the  beginning  of  an  action.  With  a 
concentration  many  thousand  times  in  its  favor  it  is  then  not  surprising 
to  find  this  very  slow  action  becoming  perceptible  in  careful  quantitative 
work.  Now,  if  we  should  use  a  much  weaker  base  still,  we  might  easily 
find  the  action  with  the  non-ionized  ester  taking  a  more  and  more  promi- 
nent part  in  the  total  change,  even  if  the  actual  rate  of  change  of  the 
positive  ester  ion  should  still  be  very  much  the  greater.  We  have  recently 
found  such  to  be  the  case  for  the  action  of  ammonia  and  ammonium 
chloride  on  benzoyl  urea  ester:2  the  velocity  constants  are  so  nicely 
balanced  against  the  affinity  constants  that  the  observed  changes  did  not 
agree  even  approximately  with  either  conception  used  alone,  viz.,  that 
the  guanidine  formation  was  due  to  the  action  of  ammonia  on  the  positive 
ester  ion  alone,  or  on  the  non-ionized  ester  alone.  But  they  did  agree 
well  with  the  view  that  both  actions  occur  simultaneously,  the  velocity 
coefficient  for  the  action  on  the  ion  being  34.5  and  the  coefficient  for  the 
action  on  the  non-ionized  ester  being  0.0015,  a  ratio  of  23000  to  i  again. 
We  were  exceedingly  pleased  to  find  this  case  because  it  forms  the  con- 
necting link  with  what  we  have  found  to  be  true  for  the  formation  of 
ordinary  acid  amides  from  acid  esters  in  the  presence  of  ammonia  and 
ammonium  salts: 

CH3COOCH3  +  NH3  — ->•  CH3CONH2  +  HOCH3  (20). 

This  action  seems  to  be  essentially  a  function  of  the  ester  and  ammonia 
and  it  is  an  extremely  slow  reaction.3  We  can  easily  understand  this 
case  now;  the  esters  as  extremely  weak  oxonium  bases  must  be  able  to 
take  only  the  faintest  traces  of  acid  from  the  ammonium  chloride  in  the 
presence  of  ammonia  and  therefore  the  slow  molecular  transformation 
comes  to  the  front  as  enormously  favored  by  the  concentrations  of  the 
reacting  components.  In  the  case  of  the  actions  of  acids  on  esters  and 
water,  the  esters  compete  only  with  an  oxonium  base  of  the  same  order 
of  strength  as  they  are  themselves  and  rather  weaker,4  the  oxonium  base 
of  water  and  here  the  reaction  with  the  ion  is  again  predominant. 

These  studies  then  show  us  a  whole  range  of  organic  compounds,  obvi- 
ously of  the  same  type  and  family  but  giving  reactions  which  proceed  quite 

1  Mr.  Norton  is  collecting  more  data  on  these  relations. 

1  J.  C.  Moore's  dissertation  (1909). 

*  Unpublished  work  by  J.  Stieglitz  and  Dr.  Barnard. 

4  Lap  worth,  Loc.  cit. 

41 


231  ON  THE   BIOCHEMISTRY   OF   NUCLEIC   ACIDS. 

differently  with  the  imido  esters  the  action  of  ammonia  on  the  positive 
ion  is  the  essential  action  and  the  use  of  a  catalytic  agent,1  an  acid  is 
advisable,  in  fact,  necessary ;  with  ordinary  esters  the  action  on  the  ion 
becomes  negligible  because  the  ion  simply  cannot  be  produced  in  sufficient 
quantity  under  these  conditions  and  the  action  of  ammonia  on  the  non- 
ionized  ester  becomes  the  essential  action.  The  addition  of  acid  as  a  catalytic 
agent  is  practically  ineffective  and  therefore  inadvisable.  But  these  ap- 
parently disconnected  results  are  now  easily  understood  as  being  per- 
fectly consistent  and  logical — the  one  case  representing  an  almost  but 
not  quite  pure  type  of  one  of  the  two  natural  simultaneous  reactions — 
the  enormously  rapid  action  of  the  ammonia  on  the  imido  ester  ion — and 
the  other  case  representing  the  almost  pure  type  of  the  other  simultaneous 
action,  the  extremely  slow  action  of  ammonia  on  the  non-ionized  ester 
molecule.  And  the  connecting  link  is  found  when  the  adjustment  of 
the  affinity  and  the  velocity  constants  involved  bring  both  actions  out 
prominently  at  the  same  time.  Of  course  one  must  then  expect  every 
possible  class  of  reactions  lying  between  these  extremes.  The  results 
show  plainly  then,  I  believe,  why  a  catalytic  agent  will  work  smoothly 
in  a  number  of  cases,  and  why  it  will  fail  utterly  in  accelerating  actions 
apparently  of  exactly  the  same  organic  type,  differing  only  in  the  numer- 
ical value  of  the  physico-chemical  constants  included  in  the  final  expres- 
sion governing  the  action  of  a  catalytic  agent.  We  have  been  using  the 
imido  esters  simply  as  a  kind  of  magnifying  glass  to  measure  all  these 
constants  and  thus  to  enable  us  to  recognize  some  of  the  general  underly- 
ing principles  which  govern  catalysis  by  such  chemical  agents,  as  acids, 
bases  and  salts. 


ON  THE  BIOCHEMISTRY  OF  NUCLEIC  ACIDS.2 

BY  P.  A.'  LEVENE. 
Received  December  2,  1909. 

Life  is  the  most  complex  phenomenon  in  nature  and  its  manifesta- 
tions are  innumerable.  They  all  mysteriously  arise  in  the  living  organism 
and  are  all  harmoniously  centered  in  it.  This,  even  in  its  simplest  form 
is  the  most  perfect  laboratory,  the  seat  of  an  infinite  number  of  chem- 
ical reactions,  none  of  them  interfering  with  the  equilibrium  of  the  others. 
The  substances  produced  by  the  most  primitive  of  the  living  organisms 
are  as  large  in  number  as  they  are  varied  in  their  properties.  The  dis- 
coveries of  new  substances  manufactured  by  the  plant  or  animal  cell 
are  not  yet  exhausted  and  for  ages  the  chemist  dreamed  of  no  better 
reward  for  his  labors  than  the  finding  in  tissue  juices  of  a  new  body  with 
properties  hitherto  unknown.  The  living  organism  was  the  only  retort, 
vital  force  the  only  reaction  in  his  possession  that  could  furnish  him  with 
carbon-containing  substances.  In  that  sense  every  chemist  in  those 
days  was  a  biological  chemist. 

In  the  year  1828  a  startling  discovery  was  announced.  Wohler  wrote 
to  Berzelius:  "I  must  tell  you  that  I  can  make  urea  without  the  aid  of 
the  kidney,  or  generally  without  the  living  organism  whether  of  man 
or  dog,"  and  four  years  later  the  divorce  of  biological  and  organic 

1  Loc  cit. 

3  Presented  at  the  Second  Decennial  Celebration  of  Clark  University,  Worcester, 
Mass.,  September  15,  1909. 

42 


ORGANIC   AND   BIOLOGICAL.  232 

chemistry  was  apparently  accomplished  when  Wohler  and  Liebig  laid 
the  foundation  of  the  organic  chemistry  of  to-day  by  their  work  on  the 
radicle  of  benzoic  acid.  However,  the  divorce  was  only  apparent,  for 
the  reason  that  only  the  knowledge  of  molecular  constitution  made  it 
possible  to  establish  the  relationship  between  the  organism  and  the 
chemical  bodies  manufactured  by  it,  only  the  knowledge  of  the  dynamics 
of  the  chemical  reactions  could  coordinate  the  observations  of  the  func- 
tions of  the  living  organism,  and  of  the  accompanying  changes  in  the 
composition  of  the  living  cells. 

The  attitude  of  the  biological  chemist  was  altered.  He  saw  his  new 
goal  in  disclosing  the  nature  of  chemical  reactions  occurring  within  the 
living  cell  and  finding  their  bearing  on  the  manifestations  of  life. 

If  time  permitted  I  would  present  to  you  the  progress  of  all  the  work 
done  in  that  direction  in  recent  years.  Within  the  narrow  limits  of  this 
report,  however,  this  is  impossible  to  accomplish  with  any  degree  of 
justice  to  the  subject  and  I  shall,  therefore,  limit  the  discussion  to  only 
one  phase,  namely,  to  the  work  bearing  on  the  chemical  interpretation 
of  one  of  the  most  cardinal  properties  of  living  matter. 

Living  matter  is  distinguished  from  inanimate  by  the  fact  that  it  under- 
goes cleavage  and  oxidation  at  a  very  perceptible  velocity,  and  that 
the  restoration  of  the  loss  sustained  in  that  manner  takes  place  at  approx- 
imately the  same  rate.  Thus  the  function  of  automatic  regeneration 
lends  to  living  matter  its  principal  peculiarity. 

Great  credit  is  due  to  the  biologist  for  the  discovery  that  in  an  or- 
ganized cell  this  function  is  seated  in  a  formation  possessing  definite 
chemical  properties,  named  chromatin  or  nuclein.  At  a  time  when 
the  process  of  regeneration  is  very  active,  namely,  during  the  develop- 
ment of  the  fertilized  egg,  the  rate  of  the  new  formation  of  nuclein  rises 
to  a  very  perceptible  degree,  and  the  observer  is  led  to  see  a  genetic  re- 
lationship between  these  two  processes. 

Our  distinguished  biologist,  Jacques  L/oeb,1  was  the  first  to  express 
the  function  of  reproduction  in  terms  of  chemical  reactions.  In  his 
address  to  the  International  Congress  of  Zoologists  held  in  Boston  in 
September,  1907,  he  stated:  "If  the  question  be  raised  as  to  what  is  the 
mo  t  obvious  chemical  reaction  which  the  spermatozoan  causes  in  the 
egg,  the  answer  must  be  an  enormous  synthesis  of  chromatin  or  nuclear 
material  from  constituents  of  the  cytoplasm."  Thus,  it  becomes  evident 
that  the  knowledge  of  the  mechanism  of  regeneration  is  dependent  on  the 
knowledge  of  the  chemistry  of  nucleins. 

I  shall  for  a  moment  forestall  the  systematic  discussion  of  the  chemical 
nature  of  nucleins  by  mentioning  that  at  the  time  of  Loeb's  address  we 
were  in  possession  of  considerable  information  on  the  composition  of 
these  substances.  It  was  known  that  phosphoric  acid  entered  into  the 
formation  of  the  molecule.  Therefore,  it  became  evident  to  Loeb  that 
a  supply  of  phosphoric  acid  was  required  in  order  to  make  a  synthesis 
of  nucleins  possible.  In  a  developing  egg  the  phosphoric  acid  was  fur- 
nished by  the  cell  itself,  for  the  formation  of  nucleins  proceeded  also 
when  the  eggs  were  placed  in  a  medium  free  of  phosphoric  acid.  The 
other  components  of  the  cell  that  are  known  to  contain  phosphoric  acid 
in  their  molecule  are  the  lipoids.  In  these  substances  phosphoric  acid 

1  University  of  California  Publications  in  Physiology,  3,  61-81  (1907). 

43 


233  ON  THE   BIOCHEMISTRY  OP  NUCLEIC  ACIDS. 

is  present  in  an  ester-form  combination,  and  Professor  Loeb  proceeded 
to  argue  that  the  first  phase  in  cell  reproduction  a  priori  ought  to  consist 
in  the  saponification  of  its  lipoids.  This  assumption  was  brilliantly  verified 
in  his  experiments  on  artificial  parthogenesis.  He  brought  to  light  the 
fact  that  dissolution  of  the  lipoids  is  actually  the  process  which  precedes 
the  nuclein  synthesis  and  the  segmentation  of  the  nucleus.  He  further 
demonstrated  that  agencies  facilitating  this  saponification  were  able  under 
favorable  conditions  to  start  the  development  of  an  unfertilized  egg 
without  the  aid  of  spermatozoa.  Thus  only  an  elementary  knowledge 
of  the  chemical  nature  of  two  cell  components  furnished  Professor  Loeb 
with  the  power  at  will  to  start  or  to  impede  cell  development  by  chemical 
means,  and  in  a  way  to  furnish  evidence  that  the  function  of  regeneration 
was  a  chemical  process.  But  the  process  of  nuclein  synthesis  in  the  ac- 
tive cells  is  not  yet  disclosed  in  its  harmonious  entirety,  and  no  one  can 
entertain  any  hope  of  arriving  at  this  knowledge  without  the  discovery 
of  the  chemical  constitution  of  nudeins. 

The  considerations  that  attracted  the  attention  of  so  many  chemists 
to  the  work  on  the  chemical  nature  of  these  substances,  therefore,  are 
becoming  very  obvious,  and  I  shall  attempt  to  present  the  results  and  the 
achievements  of  the  numerous  endeavors  towards  the  solution  of  this 
very  difficult  problem. 

The  first  important  contribution  to  the  chemistry  of  nucleins  was 
made  by  Altman,  a  biologist.1  Altman  was  in  possession  of  the  infor- 
mation that  nucleins  were  endowed  with  the  properties  of  fairly  strong 
acids,  and  further  that  they  were  quite  resistant  to  the  action  of  pepsin 
hydrochloric  acid.  The  latter  property  enabled  him  to  prepare  con- 
siderable quantities  of  nuclein  by  removing  the  protein  part  of  the  tis- 
sues by  means  of  peptic  digestion,  and  the  fats  by  the  usual  extractives. 
The  remaining  nuclein  he  found  to  consist  of  a  protein  combined  with 
a  conjugated  phosphoric  acid.  The  acid  he  named  "nucleic  acid." 
By  means  of  alkaline  hydrolysis,  Altman  succeeded  in  removing  all  the 
protein  from  his  nuclein  so  that  the  final  product  analyzed  by  him  re- 
fused to  disclose  any  trace  of  protein  even  by  the  aid  of  the  most  sensitive 
color  test. 

The  further  development  of  the  chemistry  of  nucleic  acid  was  accom- 
plished through  the  investigations  of  Miescher,  of  Schmiedeberg  and  his 
pupils,  of  Kossel  and  his  school,  by  Haiser,  G.  H.  Hammarsten  and  his 
pupil  Ivar  Bang,  and  in  this  country  by  the  work  of  T.  B.  Osborne,  of 
Walter  Jones,  and  of  my  co-workers  and  myself.  I  must,  however,  add 
that  the  purest  nucleic  acid  was  obtained  by  the  man  who  was  first  in 
so  many  lines  of  chemical  activity,  Liebig,  although  on  this  occasion 
he  failed  to  discover  the  real  significance  of  his  finding. 

I  shall  make  no  attempt  to  present  all  the  work  on  nucleic  acid  in  its 
chronological  order,  but  I  shall  refer  to  individual  investigations  in  con- 
nection with  the  discussion  of  the  development  of  the  various  phases  in 
our  knowledge  of  chemical  structure  of  those  complex  acids. 

The  three  principal  phases  in  the  endeavors  to  reveal  the  nature  of 
nucleic  acid  consist:  first,  of  work  aiming  to  obtain  the  substance  in  a 
convenient  manner,  and  in  a  possibly  unaltered  condition  with  a 

1  Arch.  Anat.  und  Physiol.  Physiol.  Abt.,  1889,  524. 

44 


ORGANIC  AND  BIOLOGICAL.  234 

view  to  ascertain  the  elementary  composition  of  the  substance;  second, 
in  the  work  directed  towards  finding  all  the  components  of  the  various 
nucleic  acids ;  and  third,  in  determining  the  actual  structure  of  the  molecule ; 
or  in  other  words  the  manner  of  arrangement  of  the  individual  com- 
ponents within  the  molecule. 

Ultimate  Analysis  of  Nucleic  Acids. 

I  shall  touch  only  briefly  on  the  first  phase  of  the  work,  for  the  reason 
that  it  is  of  interest  principally  to  the  men  personally  engaged  in  it.  The 
achievements  obtained  through  that  work  are  not  very  significant.  Only 
in  connection  with  the  study  of  inosinic  acid,  a  nucleic  acid  of  beef  muscle, 
the  elementary  analysis  was  of  unmistakable  service  in  ascertaining  the 
composition  of  the  substance.  It  was  the  first  and  thus  far  the  only 
instance  that  a  salt  of  a  nucleic  acid  was  obtained  in  a  crystalline  form. 
The  fact  that  no  other  nucleic  acid  has  been  prepared  in  an  absolutely 
pure  condition  renders  the  conclusions  drawn  from  their  analysis  only 
of  secondary  value.  The  workers  who  contributed  to  the  improvement 
in  the  methods  of  preparation  of  the  substance  are:  Altman,  Miescher, 
Schmiedeberg,  Kossel,  Neumann,  Hammarsten,  Bang,  Haiser  and  myself.1 

The  methods  of  preparation  and  of  purification  of  the  substance 
employed  by  individual  workers  differed  greatly  either  in  principle  or 
detail.  Under  such  circumstances  marked  divergence  was  noted  in 
the  analytical  figures  obtained  by  different  investigators  for  nucleic  acids 
even  of  the  same  origin.  The  following  table  illustrates  some  of  these 
discrepancies. 

TABLE  SHOWING  THE  ELEMENTARY  COMPOSITION  OP  VARIOUS  NUCLEIC  ACIDS. 

C.          H.  N.         P.          O.  Base. 

I.     Thymonucleic    acids     of     animal 
origin: 

1  Fisch  sperm: 

a  Salmon       (Miescher       and 

Schmiedeberg) 37.8  4.5  15.8  9.7  33.2  

b  Gadus  (Levene) 34.8  5.2  16.8  9.1  

c  Homo  (Katsuji  and 

Inouye) 37.5  4.4  16.0  9.7  

d  Maifisch  (Levene  and 

Mandel) 36.3     5.0     15.9     8.1       

2  Pancreas: 

a  Ivar  Bang 34.2  4.4  18.2  7.7     35.6       

b  v.  Furth,  and  Jerusalem. ..  29.2  4.3  u.6  6.9       ...     Cu  «=  14.2 

3  Spleen  (Levene) 37.8  4.8  16.5  8.99     

4  Mammary   gland    (Levene   and 

Mandel) 34.7     4.4     15.6     8.5       

5  Intestinal  wall  (Katsuji  Inouye)  37.5     4.8     15.5     9.4       

6  Thymus  gland: 

a  (Ivar  Bang) 35.8     4.2     15.3     9.3       ...     Na —    6.25 

1  Altmann,  "Uber  Nukleinsauren,"  Arch.  /.  Anat.  u.  Physiol.  Physiol.  Abt.,  1889, 
524.  Miescher,  Verhand.  der  naturforschenden  Ges.  in  Basel,  1874,  6,  138;  Arch.  exp. 
Path.  Pharm.,  37,  —  (1896).  Schmiedeberg,  Arch.  exp.  Path.  Pharm.,  43,  57  (1900). 
Kossel  u.  Neumann,  Ber.,  27,  2215,  (1894),  Neumann,  Arch.  Anat.  und  Physiol.  Physiol. 
Abt.,  1899,  552.  Bang,  Z.  physiol.  Chem.,  26, 133  (1898-9).  Haiser,  Monatsh.  Chemic, 
16.  Levene,  Z.  physiol.  Chem.,  32,  541  (1901);  37,  402  (1902-3);  45,  370  (1905). 

45 


235  ON  THE   BIOCHEMISTRY   OF   NUCLEIC  ACIDS. 

C.         H.  N  P.  O.  Base. 

b  (Kostytschew) 3* -4     4-6  12.8  7.6  ...      Ba —  17.5 

c   (Herlant) 37-534-9316.489.63     

d  (Schmiedeberg) 35.82  4. 14  14.68  9. 17     

II.  Guanylic  acid  (animal  origin): 

a  Ivar  Bang 34 .28  4.39  18.21  7.64  34.48     

b  Levene  and  Mandel 36.35  4.95  18.65  6.15  33.90     

III.  Plant  nucleic  acid: 

1  Yeast: 

a  Herlant 337     4.1     14.8     8.69     ...     Cu —       10 

b  Levene 34-97  4-4*   15.21  8.6       

2  Wheat    embryo    (Osborne    and 

Harris) 33.1     4.2     14.9     8.1        

In  adopting  an  empirical  formula  for  the  nucleic  acids  the  individual 
investigators  were  guided  not  only  by  the  analytical  figures,  but  also  by 
considerations  of  a  speculative  nature  based  to  some  extent  on  information 
obtained  on  partial  or  complete  hydrolysis  of  the  acids.  The  basis  for 
the  speculations  of  the  different  workers  varied  considerably.  This 
led  to  a  great  divergence  in  the  views  on  the  empirical  formula  of  nucleic 
acid.  The  following  table  contains  some  illustrations  of  it: 

c.    H.    N.     o.   P. 

Schmiedeberg1  (spermnucleic  acid) 40     56     14     26     4 

Stetidel2  (thymus  nucleic  acid) 43     57     15     26     4 

[54     71     20     37     5 


Levene3  (spleen  nucleic  acid) 

{43  55  15  3i  4 

Osborne  and  Harris4  (wheat  embryo  nucleic  acid) 42  62  16  31  4 

117  26  6  14  2 


Kossel5  (yeast  nucleic  acid) . 

£25     36       9     20     3 

Boas*  (yeast  nucleic  acid) 36     52     14     24     4 

Levene7  (yeast  nucleic  acid) 38     50     15     29     4 

The  Components  of  Nucleic  Acids. 

It  has  been  stated  that  the  first  knowledge  of  the  chemical  nature  of 
nucleic  acids  was  limited  to  the  information  that  it  was  a  conjugated 
phosphoric  acid.  The  first  work  of  Altmann  was  followed  by  that  of 
Kossel.  The  efforts  of  this  investigator  were  directed  towards  the  analysis 
of  the  products  of  hydrolytic  cleavage  of  nucleic  acids.  His  first  achieve- 
ment was  the  discovery  of  purine  bases  in  the  molecule  of  nucleic  acids. 
These  bases  can  be  obtained  on  cleavage  of  nucleic  acids  with  very  dilute 
solutions  of  mineral  acids.  Kossel  further  devised  methods  for  the 
separation  of  the  individual  bases.  He  arrived  at  the  conclusion  that 
four  purine  bases,  namely,  adenine,  guanine,  hypoxanthine  and  xanthine, 
enter  into  the  molecule  of  nucleic  acids.  This  view,  however,  was  later  re- 
vised as  it  was  established  that  only  two  purine  bases,  adenine  and  guanine, 
actually  enter  into  the  composition  of  nucleic  acids.  Hypoxanthine  and 

1  Arch.  exp.  Path.  Pharm.,  57,  309  (1907). 

2  Z.  physiol.  Chem.,  46,  332  (1905). 
8  Biochem.  Z.,  17,  120  (1909). 

4  Z.  physiol.  Chem.,  36,  85  (1902). 
'  Arch.  f.  Anat.  Physiol.,  p.  181  (1891). 
•  Arch    exp.  Path.  Pharm.,  55,  16  (1906). 
7  Biochem.  Z.,  17,  120  (1909). 

46 


ORGANIC  AND   BIOLOGICAL.  236 

xanthine  are  now  regarded  as  secondary  products.1  However,  it  was 
evident  from  the  figures  obtained  on  elementary  analysis  of  nucleic  acids, 
that  their  molecule  contained  substances  other  than  purine  bases.  On 
the  basis  of  the  observation  that  on  hydrolysis  with  dilute  mineral  acids 
only  the  purine  bases  are  liberated  and  the  other  components  remain 
intact,  there  was  advanced  a  theory  that  in  nucleic  acids  the  phosphoric 
acid  is  combined  with  a  complex  radicle  forming  a  conjugated  phosphoric 
acid,  and  that  this  in  its  turn  combined  with  the  purine  bases.  The 
manner  of  this  combination  was  the  subject  of  considerable  discussion 
and  disagreement. 

The  efforts  to  elucidate  the  composition  of  the  complex  radicle  resulted 
in  the  discovery  of  the  following  purine  derivatives.2 

N  =  C.NH2  HN— CO  HN— CO 

OC     CH  OC     CH  OC     C.CH3 

I      II  I      II  I      II 

HN— CH  HN— CH  HN— CH 

Cytosine.  Uracil.  Thyinine. 

However,  in  order  to  obtain  these  substances  it  was  necessary  to  resort 
to  the  hydrolysis  by  means  of  mineral  acids  of  considerable  concentra- 
tion. This  procedure  caused  many  investigators  to  express  doubt  as 
to  the  presence  of  the  pyrimidine  bases  in  the  nucleic  acid  molecule. 
The  doubt  was  particularly  great  regarding  the  orgin  of  cytosine  and 
uracil.  R.  Burian3  with  great  persistence  defended  the  view  that  these 
two  bases  took  their  origin  in  the  partial  cleavage  of  the  purine  ring. 
However,  the  majority  of  workers  were  inclined  to  consider  cytosine 
also  as  a  primary  constituent  of  the  molecule  of  nucleic  acids,  while  uracil 
was  considered  a  primary  product  in  the  acids  of  plant  origin  only. 

Besides  the  purine  and  pyrimidine  bases  the  molecule  of  nucleic  acid 
was  found  to  contain  carbohydrates.  The  complex  nucleic  acids  of 
animal  origin  contain  a  hexose,  the  exact  nature  of  which  is  not  yet 
established.  The  nucleic  acid  of  plant  origin  and  the  simpler  nucleic 
acid  of  the  animal  tissues  contain  a  pentose.  On  the  basis  of  the  work 
of  Neuberg4  the  pentose  was  considered  /-xylose.  However,  very  recently 
Jacobs  and  I  have  succeeded  in  isolating  the  substance  in  crystalline  form. 
This  made  it  possible  to  establish  the  true  nature  of  the  substance  as 
d-ribose.5 

As  the  methods  of  analysis  had  improved,  and  as  approximately  quan- 
titative estimation  of  the  components  was  made  possible,  it  was  found 
that  in  nearly  all  the  acids  the  bases  were  present  in  approximately 
equimolecular  proportions,  that  the  number  of  molecules  of  phosphoric 

1  Levene,  Z.  physiol.  Chem.,  45,  370  (1905).  W.  Jones  and  Austrian,  J.  Biol.  Chem., 
3,  i  (1907). 

2  Kossel  and  Neumann,  Ber.,  27,  2215  (J894).    Ascoli,  Z.  physiol.  Chem.,  31,  161 
(1900-1).  Kossel  and  Steudel,  Ibid.,  37,   177    (1902-3).    Levene,  Ibid.,  37,  402,  527 
(1902-3). 

*  R.  Burian,  Ergebnisse  der  Physiol.  3  Jahrg.  i  Abt.,  98  (1904);  Z.  physiol.  Chem., 
51,  438  (1907).  Steudel,  Z.  physiol.  Chem.,  53,  508  (1907).  Osborne  and  Heyl,  Am.  J. 
Physiol.,  20,  157  (1908).  Levene  and  Mandel,  Biochem.  Z.,  9,  233  (1908). 

4  Neuberg,  Ber.,  32,  3386  (1899). 

•  Levene  and  Jacobs,  Ibid.,  42,  2102,  3247  (1909). 

47 


237  ON  THE   BIOCHEMISTRY  Of   NUCLEIC  ACIDS. 

acid  corresponded  to  that  of  the  bases,  and  the  number  of  molecules  of 
carbohydrate  was  equal  to  that  of  phosphoric  acid.1 

On  the  basis  of  these  calculations,  and  on  the  basis  of  the  numbers  of 
the  character  of  the  bases  entering  into  the  molecule  of  the  individual 
nucleic  acids  the  following  classification  could  be  established: 

1.  Nucleic  acids:  Containing  one  purine  base  (no  pyrimidine),   a  pen- 
tose  and  phosphoric  acid.     (Inosinic  acid,  guanylic  acid.) 

2.  Nucleic  acids:  Containing  two  purine  bases  (guanine  and  adenine), 
two  pyrimidine  bases  (cytosine  and  uracil)  and  phosphoric  acid.    (Phy to- 
nucleic  acids.) 

3.  Nucleic  acids:  Containing  two  purine  bases  (guanine  and  adenine), 
two  pyrimidine  bases  (thymine  and  cytosine),  and  a  hexose  and  phos- 
phoric acid.     (Nucleic  acid  of  animal  tissue — thymonucleic  acids.) 

The  Constitution  of  Nucleic  Acids. 

The  early  speculations  regarding  the  constitution  of  nucleic  acids  were 
based  on  the  results  of  partial  hydrolysis  by  means  of  dilute  acids  or 
weak  alkalies.  Reference  has  been  made  already  to  the  views  expressed 
by  Kossel.2  By  mere  heating  with  water  under  increased  pressure,  this 
author  thought  he  obtained  a  substance,  which  was  free  of  purine  bases, 
but  contained  all  the  other  components  of  the  original  nucleic  acid.  The 
substance  was  named  thymic  acid.  Nucleic  acid  was  regarded  therefore 
as  a  complex  consisting  of  thymic  acid  and  of  purine  bases.  The  author 
did  not  furnish  any  detailed  information  regarding  the  nature  of  thymic 
acid.  Somewhat  more  definitely  formulated  was  the  view  of  Schmiede- 
berg.  According  to  this  author  there  existed  a  complex — nucleotin,  this 
complex  combined  with  phosphoric  acid  to  form  nucleotin  phosphoric  acid, 
and  this  acid  in  its  turn  combined  with  purine  bases  thus  forming  nucleic 
acid.  Schmiedeberg  ascribed  to  the  nucleotin  the  formula  C30H42N4O1S. 
Alsberg,3  working  in  Schmiedeberg's  laboratory,  actually  succeeded  in 
obtaining  a  substance  which  had  the  composition  of  the  hypothetic 
nucleotin.  However,  these  writers  also  failed  to  disclose  the  constitution 
of  the  complex  radicle.  In  fact,  they  failed  to  furnish  evidence  that 
their  substance  was  not  a  mixture  composed  of  several  cleavage  products 
of  nucleic  acids. 

Results  of  actual  significance  for  the  interpretation  of  the  structure 
of  the  nucleic  acid  were  obtained  only  recently.  The  point  of  de- 
parture for  the  work  was  the  study  of  inosinic  acid  by  Levene  and  Jacobs. 
As  has  already  been  pointed  out  this  acid  is  comparatively  simple  in  its 
composition.  It  is  composed  of  phosphoric  acid,  a  pentose  and  hy- 

1  Schmiedeberg,  Arch.  exp.  Path.  Pharm.,  46,  57  (1900).  Kossel  u.  Neumann, 
Ber.,  27,  2215  (1894).  Kossel  u.  Steudel,  Z.  physiol.  Ckem.,  37,  119,  120,  121,  131, 
177  (1902-3);  145,  377  (1903);  38,  49.  Ascoli,  Ibid.,  31,  161  (1900-1).  Steudel, 
Ibid.,  42,  165  (1904);  43,  402  (1905);  44,  157  (1905);  46,  332  (1905);  48,  425  (1906). 
Osborne  and  Harris,  Ibid.,  36,  85  (1902).  Jones,  W.,  and  Austrian,  /.  Biol.  Chem.,  3, 
i  (1907).  Levene,  Z.  physiol.  Chem.,  37,  402,  527  (1902-3);  38,  80  (1903);  39,  4,  479 
(1903);  43,  199  (1904);  45,  37°  (1905)-  Levene  and  Stookey,  Ibid.,  44,  404  (1904). 
Mandel  u.  Levene,  Ibid.,  46,  155  (1905);  47,  140  (1906).  v.  Furth  u.  Jerusalem,  Beitrage 
Chem.  Physiol.  u.  Pathol.,  10,  174  (1907). 

1  Kossel  and  Neumann,  Z.  physiol.  Chem.,  22,  74  (1896-7). 

3  Schmiedeberg,  Ach.  exp.  Path.  Pharm.,  43,  57  (1900).  Alsberg,  Ibid.,  51,  239 
'1904). 

48 


ORGANIC   AND   BIOLOGICAL.  238 

poxanthine.  Through  prolonged  action  of  dilute  acid  at  the  temperature 
of  50°  it  was  possible  to  break  up  the  molecule  into  hypoxanthine  and 
a  pentose-phosphoric  acid.1  This  substance  was  obtained  by  Jacobs 
and  myself  in  the  form  of  its  crystalline  barium  salt.  This  acid  had  all  the 
properties  of  a  conjugated  phosphoric  acid,  and  on  cleavage  yielded  the 
phosphoric  acid.  The  acid  reduced  Fehling's  solution  on  heating  without 
previous  hydrolysis.  It  was  concluded  from  this  that  in  the  molecule 
the  phosphoric  acid  and  the  carbohydrate  are  bound  in  ester-form,  and 
that  the  aldehyde  group  of  the  pentose  phosphoric  acid  was  free  and  that 
therefore  in  the  inosinic  acid  the  base  and  pentose  were  coupled  in  a  gly- 
coside  union.  This  assumption  was  strengthened  by  the  fact  that 
inosinic  acid  was  found  to  be  very  resistant  towards  the  action  of  alkalies 
even  at  fairly  high  temperatures,  and  even  on  prolonged  boiling  the 
acid  underwent  only  partial  hydrolysis  with  formation  of  phosphoric 
acid  and  of  the  complex:  pentose-base.  Furthermore,  it  was  found  that 
by  hydrolysis  at  nearly  neutral  point  the  conditions  for  the  reaction 
were  more  favorable  and  it  was  possible  in  this  manner  to  isolate  and  to 
identify  the  pentoside-inosine  (C^H^N^).  On  the  basis  of  this  we 
concluded  that  the  order  of  combination  of  the  components  in  the 
molecule  of  the  inosinic  acid  was  established.  I  could  add  here  that 
only  on  hydrolysis  of  the  pentoside  was  it  possible  to  obtain  the  crystal- 
line sugar  which  was  identified  as  d-ribose.  The  structure  of  the  com- 
plex pentose-hypoxanthine  may  be  represented  in  the  following  manner: 

N  — C  — N 

II       II        I 
HC 

H     H     H     H       | 

CH2OH  — C  — C  — C  — C  — N  — C      CH 
|       OH  OH    |  || 

L O  OC      NH 

The  same  substance  had  been  found  by  Haiser  and  Wenzel  in  beet 
extract.2 

Regarding  the  place  of  the  purine  base  which  entered  into  union  with 
the  sugar,  there  still  remains  only  the  evidence  of  Burian  that  place  7 
is  attached  to  the  sugar  and  no  information  exists  regarding  the  place 
of  the  hydroxyl  in  the  pentose  that  is  coupled  with  the  phosphoric  acid. 
The  following  step  in  the  progress  of  the  work  was  the  application  of 
the  experience  obtained  on  inosinic  acid  to  the  other  nucleic  acids.  Jacobs 
and  I  next  directed  our  attention  to  the  remaining  acid  of  comparatively 
simple  composition,  namely  guanylic  acid.  Employing  the  same  methods 
of  hydrolysis  as  applied  to  inosinic  acid,  we  obtained  guanosine 
(C10H13N5O5),  a  substance  analogous  to  inosine;  it  possessed  nearly  the 
same  crystalline  form,  differed  in  its  physical  constants,  and  on  hydrolysis 
gave  guanine  and  the  same  pentose  as  the  inosine,  namely  d-ribose.  This 
pentoside  had  the  same  properties  as  inosine  in  its  behavior  towards  al- 
kalies and  acids.3  For  the  sake  of  convenience  we  named  the  substances  of 
this  order  "  nucleosides "  and  the  combination  of  the  nucleoside  and  phos- 
phoric acid  we  named  "nucleotides."  Thus  according  to  that  nomencla- 
1  Ber.,  44,  2703  (1908). 

1  Haiser  and  Wenzel,  Monatsh.  Chem.,  29,  157  (1908) 
•  Ber.,  42,  2474  (1909). 

49 


239 


ON  THE   BIOCHEMISTRY  OF   NUCLEIC  ACIDS. 


ture  inosine  and  guanylic  acid  were  to  be  regarded  as  mononucleotides  of 
the  following  structure : 

N  — C  — N 


X)H 


CH 


H     H     H     H  l| 

O  =  P— O  —  CH2  —  C  —  C  —  C  —  C  —  N  —  C  —  CH 


OH 


OH  OH 
i o 

(Inosinic  acid.) 


H     H      H      H 


OC  — NH 


N  — C  — N 

!!       II       II 
CH 


O  =  P— O  — CH2  — C  — C  — C  — C  — N  — C— C— (NH2) 


\ 


OH 


OH     OH 


(Guanylic  acid.) 


OC  — NH 


The  further  application  of  the  same  methods  to  a  more  complex  nucleic 
acid,  to  that  of  the  yeast,  led  to  the  conviction  that  this  also  was  com- 
posed in  the  same  manner.  Thus  the  same  nucleoside-guanosine,  as 
obtained  from  guanylic  acid,  was  also  found  on  hydrolysis  of  the  yeast 
nucleic  acid.  When  the  proper  conditions  are  observed  the  nucleoside 
can  be  chilled  out  and  a  nearly  quantitative  separation  accomplished. 
In  the  filtrate  from  this  nucleoside  other  substances  of  the  same  nature 
were  expected.  On  the  basis  of  considerations  expressed  by  me  in  an 
earlier  article  on  the  composition  of  the  yeast  nucleic  acid  the  molecule 
of  the  acid  is  composed  of  four  nucleotides  and  therefore  four  nucleosides 
should  be  found  on  cleavage  of  the  substance.  The  work  in  that  direc- 
tion is  of  comparatively  recent  date,  and  a  second  nucleoside  has  already 
been  obtained  from  the  mother  liquor  of  guanosine.1  The  second  nucleo- 
side has  practically  the  same  crystalline  appearance  as  inosine  or  guano- 
sine,  and  differs  from  these  two  only  by  its  physical  constants  and  by 
the  fact  that  on  hydrolysis  it  yields  in  place  of  guanine  the  base  adenine, 
and  is,  therefore,  named  adenosine.  Also  on  hydrolysis  of  this  nucleo- 
side the  crystalline  d-ribose  is  obtained.  The  substance  therefore  had 
the  following  structure : 

N  — C  — N 


CH 


H      H      H     H 


CH,OH  — C  — C  — C  — C  — N  — C     CH 


OH  OH 


NH,C  =  N 


It  possesses  the  melting  point  of  229°  and  the  rotation:  [a]D  =  — 67.30°. 
On  the  ground  of  this  the  structure  of  the  yeast  nucleic  acid  may  be 
presented  in  the  following  manner  :2 

1  Levene  and  Jacobs,  Ber.,  42,  2703  (1909). 

2  Bloch,  Zeitsch.,  120,  17  (1909). 


ORGANIC   AND   BIOLOGICAL. 


240 


OH  H      H     H 

O  =  P  — O  —  CH3  —  C  —  C  —  C  —  CH  —  C6H4N5 
|    OH  OH      | 

O  J O 

H     H     H 

O  =  P  —  0  —  CH,      C  — C  — C  — CH  — C5H4N5O 
|    OH  OH      |! 

OH  J O 

All  this  work  is  of  comparatively  recent  date  so  that  as  yet  it  could 
not  have  been  extended  to  the  analysis  of  thymonucleic  acid.  But 
evidence  had  been  furnished  that  this  substance  also  has  a  structure 
analogous  to  that  of  the  yeast  nucleic  acid.1  In  fact  considerations 
based  on  the  work  on  thymus  nucleic  acid  were  the  first  that  led  to 
formulating  the  structure  of  the  complex  nucleic  acid  as  a  polynucleotide, 
of  which  the  individual  mononucleotides  were  composed  of  phosphoric 
acid,  sugar  and  base.  Levene  and  Mandel  have  on  hydrolysis  of  the 
spleen  nucleic  acid  with  dilute  sulphuric  acid  obtained  a  substance  which 
had  the  elementary  composition  (CUH17N2PO10)  of  a  complex  consisting 
of  phosphoric  acid,  hexose  and  thy  mine.  On  cleavage  with  25  per  cent, 
sulphuric  acid  this  body  gave  rise  to  phosphoric  acid,  levulinic  acid  and 
thymine.  This  assumption  is  in  harmony  with  subsequent  discoveries 
on  the  simple  nucleic  acid  and  on  the  yeast  nulceic  acid,  and  one  feels  justi- 
fied in  formulating  the  structure  of  thymonucleic  acid  in  the  following 
manner : 

OH     H  OH  OH     H 
O  — CH2  — C  — C  — C  — C  — C- 


O  =  P— OH 


H 


H      H 


C5H4NS 


-O 

N 


/~  OH      H  OH  OH 

=  P— O  —  CH,  —  C  —  C  —  C  —  C  —  C—  C5H4N6O 


OH 


H 


H     H 


-O 


Thus  the  details  in  the  structure  of  the  molecule  of  nucleic  acids  are 
not  yet  known.  But  some  general  information  is  already  obtained  and 
the  route  is  singled  out,  by  which  the  solution  of  the  problem  will  be 
reached.  An  indication  is  given  for  a  point  of  departure  for  the  work 
on  the  synthesis  of  these  substances.  Work  in  that  direction  is  now  in 
progress  in  our  laboratory. 

THE  ROCKEFELLER  INSTITUTE  FOR  MEDICAL  RESEARCH, 
NEW  YORK  CITY. 


THE  FUNDAMENTAL  LAW  FOR  A  GENERAL  THEORY  OF 

SOLUTIONS.1 

BY  EDWARD  W.  WASHBURN. 
Received  March  3,  1910. 

Nomenclature. 

C  Volume  concentration. 

(i)  Cp,  (2)  Cp  Molecular  heat  capacity  of  (i)  a  liquid,  (2)  a  gas. 

ACp  Decrease  in   molecular  heat  capacity  attending  a  change  in 

state  of  aggregation, 
(i)  KC,  (2)  KN  Equilibrium  constant  in  terms  of  (i)  volume  concentrations, 

(2)  mol  fractions.     (Products  of  the  reaction  in  the  denomi- 
nator.) 

KS  Solubility  product  in  terms  of  mol  fractions, 

(i)  LS  (2)  Lg  (3)  Lp    Molecular  heat  of  (i)  sublimation,  (2)  vaporization,  (3)  fusion 

(under  constant  external  pressure). 

(i)  N,  (2)  N'  Mol  fraction  of  (i)  solvent,  (2)  solute, 

(i)  n,  (2)  n'  Number  of  mols  of  (i)  solvent,  (2)  solute. 

p  Gas  or  vapor  pressure. 

P  External  pressure  on  a  liquid  or  solid. 

Qx  Heat  evolved  when  the  reaction  aA  +  bB  +  ....  =  mM.  + 

»N  +  . . . .    takes   place   from   left   to   right   in  a  solution 

under  osmotic  equilibrium. 
R  Gas  constant. 

(i)  T,  (2)  Tp,  (3)  T0,  (i)  Absolute   temperature,    (2)    absolute    temperature   of   the 
(4)  TB,  (5)  TBO  freezing  point  of  a  solution,  (3)  of  the  freezing  point  of  the 

pure  solvent,  (4)  of  the  boiling  point  of  a  solution,  (5)  of  the 

boiling  point  of  the  pure  solvent. 
U  Total  energy  decrease  produced  when  the  reaction  aA.  +  bE  + 

. . . .  =  mM.  +  nN  +  . . .  takes  place  from  left  to  right. 
(i)  v,  (2)  V  Molecular  volume  of  (i)  a  gas,  (2)  a  liquid. 

JT  Osmotic  pressure. 

p.  Thermodynamic  potential. 

tf>  Fugacity. 

6  Activity. 

I.  The  Development  of  the  Modern  Theory  of  Solutions. 

Upon  the  foundations  laid  by  the  labors  of  van't  Hoff  and  Arrhenius 
has  arisen  the  structure  which  we  know  to-day  as  the  Modern  Theory  of 
Solutions.  Before  van't  Hoff's  epoch-making  discovery  of  the  ther- 

1  Presented  at  the  Second  Decennial  Celebration  of  Clark  University,  Worcester, 
Mass.,  September  16,  1909. 

52 


GENERAL,    PHYSICAL    AND    INORGANIC.  654 

modynamic  relations  which  bind  together  the  colligative  properties2  of 
dilute  solutions,  our  knowledge  concerning  these  important  quantities 
was  confined  to  a  set  of  apparently  unconnected  empirical  laws.  Van't 
Hoff's  generalization  of  these  laws,  followed  almost  immediately  by  the 
Ionic  Theory  of  Arrhenius,  stimulated  greatly  the  study  of  solutions  and 
made  possible  the  rapid  development  and  perfection  of  our  present  theory. 
Investigation  has,  however,  been  confined  chiefly  to  the  domain  of  dilute 
solutions  and  the  Modern  Theory  of  Solutions  has  remained  almost  en- 
tirely a  theory  of  dilute  solutions.  The  reason  for  this  is,  I  believe,  due 
largely  to  one  of  those  historical  "accidents"  which  occur  now  and  then 
in  the  development  of  science.  The  history  of  this  "accident"  and  the 
manner  in  which  it  came  about  forms  a  chapter  in  physical  chemistry  of 
interest  alike  to  the  chemist  and  to  the  philosopher. 

Perhaps  the  best  way  to  form  a  clear  idea  of  the  process  of  evolution 
of  our  present  theory  of  solutions  is  to  consider  first  the  colligative  prop- 
erties of  solutions  and  the  relations  which  connect  them.  These  quan- 
tities— the  osmotic  pressure,  vapor  pressure,  freezing  point,  boiling  point, 
etc. — have  played  such  an  important  and  vital  part  in  the  development  of 
our  solution  theory  that  a  clear  idea  of  their  relations  to  one  another  is 
absolutely  essential  to  a  proper  understanding  of  the  theory  and  of  its 
development.  The  nature  of  these  relations  is  expressed  by  the  follow- 
ing statement :  The  colligative  properties  of  a  solution  are  connected  by  a  set  of 
rigorous  differential  equations  which  involve  no  assumptions  except  the  two 
laws  of  thermodynamics.  The  equations  are  as  follows: 


(1)  Osmotic  Pressure  and  Freezing  Point, 

dTF 
V~ 

(2)  Vapor  Pressure  and  Freezing  Point, 


/—  LF\ 

=  [  —  -  (82) 

\    V    >         - 


(92) 
(3)  Osmotic  Pressure  and  Vapor  Pressure, 

(77) 


(4)  Osmotic  Pressure  and  Boiling  Point, 

'L. 


(90) 

To  these  should  be  added  a  number  of  others,  such  as  the  relation  be- 
tween the  electromotive  force  of  a  concentration  cell  and  either  vapor 
pressure  (74)  or  osmotic  pressure  (70),  and  (16  and  14)  the  mutual  re- 
lations among  the  osmotic  pressures  or  vapor  pressures  of  the  constituents 
of  a  physical  mixture  or  (30  and  300)  the  substances  concerned  in  a 

2  Following  Ostwald,  the  term  "colligative  properties"  is  used  to  embrace  such 
properties  as  osmotic  pressure,  boiling  point  raising,  freezing  point  lowering,  vapor 
pressure  lowering,  etc. 

53 


655  FUNDAMENTAL  LAW  FOR  THEORY  OF  SOLUTIONS. 

chemical  equilibrium,  etc.3  While  the  following  discussion  applies  with 
equal  force  to  all  of  these  relations,  it  will  perhaps  be  conducive  to  clear- 
ness, if  we  confine  our  attention  chiefly  to  the  four  relations  given  above. 

From  the  method  of  derivation  of  these  relations,  it  is  clear  that  they 
do  not  involve  any  assumptions  regarding  the  concentration  of  the  solu- 
tion, nor  do  they  depend  in  any  way  upon  the  nature  of  the  dissolved 
solute  or  its  degree  of  association,  dissociation,  or  solvation.  In  fact,  if 
one  knows,  for  example,  the  vapor  pressure,  freezing  point  lowering  or 
boiling  point  raising  for  a  solution  of  any  nonvolatile  solute,  he  has  the 
means  of  calculating  the  osmotic  pressure  for  the  same  temperature  with- 
out knowing  either  the  concentration  of  the  solution  or  the  nature  of  the 
solute.  There  may  be  one  or  several  solutes  present  and  they  may  as- 
sociate, dissociate,  or  unite  with  each  other  or  with  the  solvent  in  any 
manner  and  to  any  extent.  These  questions  are  in  no  way  involved  in 
the  calculation.  Since  relations  such  as  those  existing  among  the  collig- 
ative  properties  of  a  solution  involve  only  the  two  laws  of  thermody- 
namics, it  will  be  convenient  to  refer  to  them  as  "purely  thermodynamic 
relations"  to  distinguish  them  from  an  important  group  of  relations  which 
involve  the  composition  of  the  solution  and  the  nature  of  its  components, 
and  which  we  will  now  proceed  to  consider. 

Let  us  consider  a  solution  of  any  solute  A  in  any  solvent  B,  and  let  our 
problem  be  to  express  each  of  the  colligative  properties  of  the  solution 
as  a  function  of  its  composition  or  its  "concentration."  This  problem 
can  in  general  be  solved  only  by  direct  experiment  for  the  particular 
solvent  and  solute  under  consideration.  From  what  has  preceded,  how- 
ever, it  is  evident  that  as  soon  as  we  know  the  relation  between  any  one 
of  the  colligative  properties  and  the  composition  of  the  solution,  the  other 
relations  become  thereby  determined.  If,  for  example,  we  determined 
the  freezing  point  of  the  solution  for  a  series  of  concentrations,  we  could 
calculate  thermodynamically  the  osmotic  pressure,  the  vapor  pressure, 
etc.,  for  the  same  concentrations  and  thus  derive  an  equation  connecting 
each  of  these  quantities  with  the  concentration.  The  colligative  property 
which  should  be  chosen  for  experimental  study  in  a  given  case  would 
depend  upon  the  relative  ease  and  accuracy  with  which  the  several  quan- 
tities could  be  determined  and  the  temperature  range  which  it  was  desired 
to  cover;  also  in  some  cases  upon  whether  the  requisite  "caloric  quan- 
tities"4 were  known  with  sufficient  accuracy  or  could  be  determined  readily. 

The  relation  between  any  one  of  the  colligative  properties  and  the  con- 
centration of  the  solution  for  any  given  solvent  and  solute  will  obviously 
depend  upon  the  degree  of  association,  dissociation  and  solvation  of  the 
solute.5  Since  the  magnitude  of  these  effects  and  their  dependence  upon 

3  The  derivations  of  these  relations  and  a  more  detailed  discussion  of  them  are 
given  in  a  previous  paper,  "A  Simple  System  of   Thermodynamic   Chemistry  Based 
upon  a  Modification  of  the  Method  of  Carnot"   (Tins  JOURNAL,  32,  467  (1910)).     For 
convenience  in  reference  these  equations  are  given  the  same  number  here  as  in  the 
previous  paper  where  the  significance  of  the  quantities  appearing  in  the  equations  is 
explained  in  detail. 

4  Proposed  by  van  der  Waals  to  distinguish  heat  capacities,  latent  heats,  heats  of 
reaction,  etc.,  from  colligative  properties. 

5  It  is  hardly  necessary  to  remark  that  this  statement  tacitly  assumes  that  the 
desired  relation  is  to  be  one  which  involves  the  number  of  mols  of  the  solute. 

54 


GENERA!,,    PHYSICAL   AND   INORGANIC.  656 

the  concentration  are  in  general  unknown  quantities,  the  problem  is  too 
complex  for  any  complete  solution.  In  general,  therefore,  it  is  necessary 
to  make  a  separate  investigation  for  every  solvent  and  solute  in  order  to 
establish  the  desired  relation  connecting  some  one  of  the  colligative  proper- 
ties with  the  concentration.  To  leave  the  problem  in  this  condition,  how- 
ever, is  naturally  not  very  satisfactory,  and  the  course  usually  followed 
by  science  when  confronted  with  a  problem  which  is  too  complex  is  first 
to  simplify  the  problem.  Let  us  try  to  trace  the  process  of  simplification 
which  has  been  followed  by  science  in  the  present  instance. 

Since  association  or  dissociation  of  either  solvent  or  solute  molecules 
introduces  complications,  the  first  step  in  the  process  of  simplification  is 
obviously  to  consider  the  simple  case  of  a  solution  in  which  neither  takes 
place.  Since  the  union  of  a  portion  or  all  of  the  solute  molecules  with 
the  solvent  molecules  (solvation)  is  also  a  complicating  factor,  the  next 
step  in  the  process  of  simplification  would  naturally  be  to  eliminate  this 
factor  also  by  assuming  no  solvation.  After  making  these  simplifications 
our  problem  would  read  as  follows:  What  are  the  relations  connecting 
the  colligative  properties  with  the  composition  in  the  case  of  a  solution 
in  which  the  number  of  molecular  species  present  is  equal  to  the  number 
of  components?0  Let  us  call  such  a  solution,  provisionally,  an  "ideal 
solution,"  postponing  until  later  a  more  definite  and  accurate  description 
of  the  properties  of  the  type  of  solution  to  which  the  term  "ideal"  should 
be  applied. 

There  is,  however,  another  method  by  which  the  complicating  factor 
of  solvation  can  also  be  eliminated.  Willard  Gibbs,  in  his  monumental 
work  on  thermodynamic  chemistry,  has  taught  us  that  the  proper  way 
to  represent  the  composition  of  any  phase  is  by  the  means  of  the  mol 
fractions  of  its  several  components.7 

Now  in  the  case  of  a  solution,  the  mol  fraction  of  the  solute  (for  ex- 
ample) will  be  altered  if  it  becomes  solvated  on  going  into  solution,  owing 
to  the  consequent  change  in  the  number  of  solvent  molecules.  Such  a 
complication  can  be  eliminated  from  our  problem,  as  explained  above, 
by  assuming  no  solvation;  or  it  can  be  likewise  eliminated  by  taking  the 
solution  sufficiently  dilute.  For,  as  the  solution  becomes  more  and  more 
dilute,  the  limit  approached  by  the  mol  fraction  of  the  solute  is  the  same 
whether  solvation  occurs  or  not.8 

*  For  example,  in  the  case  of  two  components,  a  solvent  and  one  solute,  there 
would  be  only  two  different  kinds  of  molecules;  for  a  solvent  and  two  solutes,  only 
three  different  kinds  of  molecules,  etc. 

7  This  system  has  been  consistently  followed  by  all  investigators  who  use  systems 
of  thermodynamics  based  upon  Gibbs'  thermodynamic  potential.     The  reason  that  it 
has  not  been  followed  by  others  is  because  they  have  confined  themselves  to  the  region 
of  dilute  solutions,  where  it  is  possible  to  use  one  of  the  limiting  forms  approached  by 
the  mol  fraction  of  the  solute,  as  the  concentration  approaches  zero. 

8  To  illustrate,  if  we  put  n'  mols  of  a  solute  in  n  mols  of  a  solvent  and  no  solvation 

n' 

(or  dissociation  or  association)  occurs,  then  the  mol  fraction  of  the  solute  is 

(n'  +  n) 

If,  however,  on  the  average  x  mols  of  solvent  are  combined  with  each  mol  of  solute, 

n'  n' 

the  mol  fraction  of  the  (solvated)  solute  is or .     As  the 

[n'  +  n  —  n'x]        \n'(i—x)  +  n] 

55 


657  FUNDAMENTAL  LAW   FOR  THEORY   OF   SOLUTIONS. 

Owing  to  an  "historical  accident"  the  latter  method  of  eliminating  the 
complication  of  solvation  has  been  the  one  followed  by  science,  instead  of 
the  former  and  more  logical  one.  The  "historical  accident"9  in  this 
instance  was  van't  Hoff's  brilliant  discovery  of  the  remarkably  simple 
equation  connecting  osmotic  pressure  with  temperature  and  concentration 
in  very  dilute  solutions.  Starting  with  this  equation  as  a  basis  and  using 
the  principles  of  thermodynamics,  he  showed  us  how  to  construct  a  com- 
plete theory  of  dilute  solutions. 

As  the  field  of  dilute  solutions  became  more  and  more  developed,  both 
from  the  experimental  and  theoretical  side,  investigators  began  to  turn 
their  attention  to  the  subject  of  concentrated  solutions.  Investigation 
in  this  direction  has  usually  taken  the  direction  of  attempts  to  extend  the 
osmotic  pressure  equation  by  the  introduction  of  quantities  corresponding 
to  the  a  and  b  of  van  der  Waals'  condition  equation  for  gases,  upon  the 
basis  of  kinetic  conceptions  derived  from  an  assumed  analogy  between 
osmotic  and  gas  pressure.  Other  investigators  have  sought  to  attribute 
all  of  the  deviation  of  concentrated  solutions  from  the  equations  of  dilute 
solutions,  to  solvation,  and  have  even  gone  so  far  as  to  compute  on  this 
basis  the  approximate  degree  of  hydration  in  some  very  concentrated 
aqueous  solutions,  for  example.  Still  other  attempts  have  been  taken  in 
the  direction  of  an  extension  of  our  present  equations  by  the  addition  of 
a  series  of  terms  containing  a  number  of  constants  intended  to  express 
the  influence  of  the  solute  molecules  upon  one  another  and  upon  the 
solvent. 

Attempts  to  obtain  a  satisfactory  theory  of  concentrated  solutions  in 
any  of  these  directions  give  no  promise  of  success.  An  attempt  to  "ex- 
plain" why,  as  a  solution  becomes  more  and  more  concentrated,  it  de- 
viates more  and  more  from  the  equations  of  very  dilute  solutions  is  some- 
what analogous  to  an  attempt  to  explain  why  the  sine  of  angle,  which 
for  sufficiently  small  angles  is  equal  to  the  angle,  deviates  more  and  more 
as  the  angle  grows  larger.  The  reason  is,  of  course,  a  purely  mathematical 
one.  Similarly  in  the  case  of  solutions  there  is  first  of  all  a  purely  mathe- 
matical reason  why  concentrated  solutions  should  deviate  from  the  equa- 
tions of  the  infinitely  dilute  solution.  The  equations  of  dilute  solutions 
are  the  limiting  forms  assumed  by  more  general  equations,  owing  to  the 
fact  that  certain  terms  become  negligible  as  the  concentration  approaches 
zero.  In  other  words  we  have  in  our  dilute  solution  laws  only  a  portion, 
the  residue,  so  to  speak,  of  a  more  general  set  of  laws  for  solutions  of  all 

solution  becomes  more  and  more  dilute,  both  expressions  approach  -   as  their  limit. 

n 

This  is  the  familiar  ratio  which  appears  in  our  boiling  point  and  freezing  point  equations. 

(n'\  (RT\ 

In  the  case  of  our  osmotic  pressure  equation,  instead  of  writing  it  jr==l~)\  —  ) » 

\n  /  \  r  / 

where  V  is  the  molecular  volume  of  the  solvent,  it  is  customary  to  substitute  Vs  =» 
nV  and  write  nVs  =  n'RT.  Here  again,  if  the  solution  is  sufficiently  dilute,  it  is  ob- 
viously immaterial  whether  we  understand  Vt  to  mean  the  volume  of  the  solution  or 
the  volume  of  pure  solvent  in  which  the  n'  mols  of  solute  were  dissolved  in  preparing 
the  solution. 

*  The  expression,  "historical  accident,"  is,  of  course,  used  in  the  philosophical 
sense. 

56 


GENERAL,    PHYSICAL    AND   INORGANIC.  658 

concentrations.  Consequently  before  science  can  hope  to  make  any 
progress  in  the  region  of  concentrated  solutions  she  must  go  back  to  the 
point  where  the  simplifying  assumption  of  a  dilute  solution  was  uncon- 
sciously introduced,  and,  in  place  of  it,  make  the  simplifying  assumption 
of  an  "ideal  solution"  as  we  have  denned  it  above.  We  come,  therefore,  to 

2.  The  Laws  of  the  Ideal  Solution. 

Owing  to  the  simplicity  of  the  thermodynamic  treatment  of  solutions 
by  what  we  may  call  the  osmotic-cyclical-process  method  and  the  fact 
that  it  uses  conceptions  which  are  comparatively  easy  to  grasp  and  pro- 
cesses which  can  be  readily  pictured  in  the  mind,  it  has  been  the  favorite 
system  among  physical  chemists.  The  fact  that  the  theories  developed 
by  the  advocates  of  this  method  have  been  confined  almost  entirely  to 
the  domain  of  the  dilute  solution  is  not  due  to  any  inherent  fault  in  the 
method.  In  addition  to  this  method  we  have  the  systems  of  thermody- 
namics based  upon  the  Gibbs  thermodynamic  potential  and  its  related 
functions.  These  systems  have  been  the  favorite  ones  among  physicists 
and  those  who  by  training  and  inclination  were  accustomed  to  the  use  of 
potential  functions,  and  it  is  among  the  advocates  of  the  thermodynamic 
potential  that  we  find  the  first  successful  attempt  to  formulate  a  theory 
of  solution  which  is  free  from  the  assumption  that  the  solution  must  be 
dilute. 

This  theory  has  been  developed  in  Holland  by  van  der  Waals  and  his 
associates,  especially  by  van  Laar.  The  first  attempt  was  made  in  1893 
by  Hondius  Boldingh10  in  an  Amsterdam  Dissertation  which  so  far  as  I 
have  been  able  to  learn  has  never  been  published  elsewhere.  In  the 
following  year  van  Laar11  published  two  papers  in  which  he  derived  a  set  of 
"exact  formulae  for  osmotic  pressure,  change  in  solubility,  freezing  point, 
boiling  point,  etc."  His  results  were  expressed  in  a  series  of  equations 
in  which  the  concentration  of  the  solution  appeared  in  a  term,  In(i-N'), 
in  which  N'  represents  the  mol  fraction  of  the  solute.  The  equations 
contained,  in  addition,  an  undetermined  function  of  the  molecular  ther- 
modynamic potentials  of  the  constituents.  In  numerous  subsequent 
publications  van  Laar  has  advocated  with  great  warmth  and  zeal,  the 
use  of  the  thermodynamic  potential  method  and  the  introduction  of  the 
concentration  of  the  solution  into  the  equations  by  means  of  the  expression 
ln(i-A7/),  instead  of  assuming  that  the  solution  is  dilute.  Van  Laar  has 
in  fact  advocated  a  theory  of  solution  which  is  entirely  free  from  the 
assumption  that  the  solution  must  be  dilute.  The  foundations  for  this 
theory  have  existed  in  the  literature  for  the  last  fifteen  years.  If  it  occurs 
to  any  one  to  wonder  why  the  theory  has  not  come  into  general  use  in  the 
chemical  world,  he  has  only  to  glance  through  some  of  van  Laar's  papers, 
especially  his  earlier  ones,  and  the  reason  will  be  more  or  less  obvious. 

It  is  my  present  purpose  to  free  this  theory  from  the  language  of  the 
thermodynamic  potential  and  to  develop  it  in  the  so-called  "osmotic 
language."12  Stated  in  this  language,  our  problem  is  to  determine  the 

10  Boldingh,  "De  Afwijkingen  van  de  Wetten  voor  Verdunde  Oplossingen."     Dis- 
sertation, Amsterdam,  1893. 

11  van  Laar,  Z.  physik.  Chem.,  15,  457  (1894). 

12  The  "language  of  the  colligative  properties"   would  be  a  better  term.     Too 
much  importance  is  usually  ascribed  to  osmotic  pressure  in  our  solution  theory. 

57 


659  FUNDAMENTAL  LAW   FOR   THEORY   OF   SOLUTIONS. 

functional  relation  between  some  one  of  the  colligative  properties  of  the 
solution  and  its  concentration  in  the  case  of  an  ideal  solution.  Theoreti- 
cally we  can  start  with  any  one  of  the  colligative  properties  we  choose,  but 
since  our  present  theory  of  dilute  solutions  is  usually  assumed  to  start 
with  the  osmotic-pressure-concentration  relation,  it  will  perhaps  be  more 
interesting  to  develop  our  theory  of  the  ideal  solution  from  the  same 
standpoint. 

Let  us,  therefore,  turn  to  the  equation  which  expresses  the  osmotic 
pressure13  for  a  very  dilute  solution : 

_  n'RT  _  n'RT 
~T7     "~nV 

In  this  equation,  n'  is  the  number  of  mols  of  solute  in  n  mols  of  solvent 
and  V  is  the  molecular  volume  of  the  pure  liquid  solvent.  Let  us  now 
make  use  of  the  method,  introduced  by  Willard  Gibbs,  of  expressing  the 
composition  of  the  solution  by  means  of  the  equation  N'  +  N  =  i ,[  where 
N'  is  the  mol  fraction  of  the  solute  and  N  that  of  the  solvent.  The 
above  equation  can  now  be  written : 


RT 


n'  N'RT 


n  +  n' 


We  have  long  recognized  the  fact  that  our  osmotic  pressure  equation 
expresses  strictly  only  the  limit  approached  by  the  osmotic  pressure  as 
the  concentration  of  the  solution  approaches  zero.  Let  us  therefore 
write  the  equation  itself  so  that  it  will  indicate  this  fact.  This  gives  us 

(*N'\(RT\ 

V1TAT/- 

Seeing  the  equation  in  this  form  it  is  natural  to  suspect  that  the  real 
relation  might  possibly  be 

dN'\  fRT\ 

AT  AT/'  (I°3) 

or  since  by  definition — dN'  =  dN, 

ft'p\ 

-—Jd\nN.  (104) 

Stated  in  words,  this  means  that  not  only  would  the  addition  of  dN'  mols 
of  solute  to  a  pure  solvent  involve  an  increase  (i.  e.,  from  o  to  ATT)  of 
osmotic  pressure  which  satisfies  equation  (104)  but  that  it  would  also 
involve  the  same  increase  in  osmotic  pressure  when  added  to  a  solution 
whose  osmotic  pressure  is  TT.  If  such  proves  to  be  the  case  (and  we  shall 
see  that  in  many  cases,  at  least,  it  does) ,  our  Modern  Theory  of  Solutions 

13  Throughout  this  paper,  we  shall  understand  by  the  term  "osmotic  pressure," 
the  pressure  difference  TT  as  defined  by  the  equation  TT  =  P  —  PA,  where  PA  is  the 
pressure  upon  the  pure  liquid  solvent  A  when  it  is  in  equilibrium  (through  a  membrane 
or  medium  permeable  only  to  itself)  with  the  solution  under  the  constant  pressure  P. 
This  has  been  discussed  more  fully  in  the  previous  paper  (Tins  JOURNAL,  32, 478  (1910)). 

58 


GENERAL,    PHYSICAL    AND   INORGANIC.  660 

has  remained  a  theory  of  infinitely  dilute  solutions,  because  we  have 
failed  to  recognize  the  fact  that  we  have  been  working  with  true  differen- 
tial equations,  and  that  in  order  to  obtain  the  "theory  of  concentrated 
solutions"  which  we  have  been  seeking,  the  only  thing  we  needed  to  do  was 
to  integrate  our  equations. 

In  the  case  of  osmotic  pressure,  for  example,  if  we  integrate  equation 
(104),  we  shall  obtain  an  equation  which  contains  no  assumption  whatever 
regarding  the  concentration.  The  solution  may  be  infinitely  dilute  or 
infinitely  concentrated  or  may  have  any  concentration  between  these 
limits.  In  order  to  do  this  we  have  only  to  put  V  =  V0(i  +  OTT),  where 
V0  is  the  molecular  volume  of  the  pure  solvent  under  the  standard  pres- 
sure P  and  a  is  its  coefficient  of  compressibility,  and  on  integration  we 
obtain  the  Boldingh-van  Laar1*  equation  for  osmotic  pressure: 


_  '!DfTt\ 

—  —  Jln(i  — 

*    O        * 


(105) 


Having  come  to  the  conclusion  that  the  integral  of  equation  (104)  should 
represent  the  osmotic  pressure  for  an  "ideal  solution,"  whatever  its  con- 
centration, we  naturally  seek  for  experimental  confirmation  before  adopt- 
ing it  finally.15  Owing  to  the  great  difficulty  of  making  accurate  and 

14  The  history  of  this  equation  (105)  is  very  interesting.     The  differential  form 
as  expressed  by  equation  (104)  was  obtained  by  van  der  Waals  as  early  as  1890  (Z. 
physik.  Chem.,  5,  163)  but  no  attempt  was  made  to  integrate  it,  only  the  case  of  dilute 
solutions  being  discussed,  for  which  case  it  assumes  the  form  of  equation  (102)  or 
(100).     In  1893  Hondius  Boldingh,  a  student  of  van  der  Waals,  making  use  of  the 
thermodynamic  potential  of  Gibbs,  derived  equation  (105)  in  the  following  form  (Diss.» 
Amsterdam,  1893,  p.  57): 

xV0  =  —RT  In  (i  —  N1)  +  aN' 

This  differs  from  equation  (105)  as  we  have  obtained  it  above,  only  in  the  fact  that 
the  compressibility  of  the  liquid  is  neglected  and  a  small  correction  term  aN'  is  added, 
a  being  a  quantity  which,  according  to  the  molecular  theory  of  van  der  Waals,  expresses 
the  mutual  influence  of  the  components  of  the  solution  upon  each  other.  For  "ideal 
solutions"  it  is  negligible. 

Boldingh  apparently  made  no  attempt  to  apply  his  equation.  The  same  equation 
was  obtained  the  following  year  by  van  Laar  (Loc.  cit.)  and  in  numerous  publications 
since  then,  this  investigator  has  given  various  derivations  of  this  equation  usually  by 
methods  involving  the  thermodynamic  potential  (cf.,  however,  note  15).  In  1897 
an  osmotic  pressure  equation  in  its  essential  points  practically  identical  with  equation 
(105)  was  derived  by  Willard  Gibbs  (Nature,  60,  461  (1897))  by  a  method  of  balanced 
columns.  Finally  G.  N.  Lewis,  in  a  recent  paper  (Tins  JOURNAL,  30,  675  (1908)),  has 
obtained  equation  (105)  by  a  derivation  involving  his  "activity"  function  and  based 
upon  the  assumption  that  the  "activity"  of  the  solvent  is  proportional  to  its  mol 
fraction.  Both  van  Laar  (Proc.  Acad.  Sci.,  Amsterdam,  9,  55  (1906))  and  Lewis 
(Loc.  cit.)  have  discussed  the  relation  of  this  equation  to  the  van't  Hoff  equation  and 
have  made  comparisons  of  the  values  of  osmotic  pressure  given  by  it  with  those  obtained 
by  Morse  and  Fra/.er  by  direct  measurement,  in  the  case  of  aqueous  solutions. 

15  In  view  of  the  fact  that  the  van't  Hoff  equation  for  osmotic  pressure  is  usually 
regarded  as  derivable  from  the  kinetic  theory  by  methods  analogous  to  those  used  in 
the  kinetic  derivation  of  the  perfect  gas  laws  (that  is,  on  the  assumption  that  osmotic 
pressure  is  caused  by  the  molecular  bombardment  of  the  solute  molecules),  it  may 

59 


66  1  FUNDAMENTAL  LAW   FOR  THEORY   OF   SOLUTIONS. 

reliable  osmotic  pressure  measurements,  it  would  be  an  unnecessary 
waste  of  time  and  effort  to  seek  experimental  confirmation  in  this  direc- 
tion, especially  as  the  equation  can  be  tested  just  as  satisfactorily  by  means 

not  be  without  interest  to  include  here  a  brief  kinetic  derivation  of  the  differential 
form  of  equation  (105).  For  this  purpose  I  shall  modify  slightly  the  derivation  given 
by  van  Laar  (Sechs  Vortrage,  p.  20). 

Consider  two  solutions  of  the  same  solute  in  the  same  solvent,  both  under  the  ex- 
ternal pressure  P  and  separated  from  each  other  by  a  membrane  permeable  only  to  the 
molecules  of  the  solvent.  According  to  a  theorem  of  Boltzmann,  the  number  of  solvent 
molecules  which  diffuse  per  second  through  a  unit  surface  of  the  membrane  in  the 
two  directions  is  given  by  the  expressions: 

(a)  From  the  weaker  solution  to  the  stronger, 


UTB  =  (i—N'w)e—RT~  (  107) 

(6)  From  the  stronger  solution  to  the  weaker, 

i+PVf 

ns  =  (/  —  N'f)e~Rf-  •  (  108) 

In  these  equations  e  is  the  base  of  natural  logarithms,  N'w  and  N's  are  the  mol  frac- 
tions of  solute  in  the  weaker  and  the  stronger  solutions  respectively,  V  is  the  volume 
of  the  solution,  R  the  gas  constant,  T  the  absolute  temperature  and  A  a  quantity 
which  is  a  function  of  the  temperature  and  which  depends  upon  the  units  of  measure- 
ment. By  adjusting  the  pressure  on  the  two  solutions  we  can  make  the  number  of 
molecules  of  solvent  which  pass  in  the  two  directions  equal  ;  in  other  words  the  two  solu- 
tions will  be  in  equilibrium  as  respects  the  passage  of  the  solvent  from  one  to  the 
other.  Under  these  conditions  the  right-hand  members  of  the  above  equations  can  be 
placed  equal  to  each  other,  giving  us  the  equation: 


Or  - 

Let  us  now  impose  the  condition  that  the  "weaker  solution"  shall  be  the  pure 
solvent  and  that  the  "stronger  solution"  shall  be  an  infinitely  dilute  solution  in  this 
solvent  and  shall  be  under  an  external  pressure  P.  Under  these  conditions  the  above 
equation  assumes  the  form 


(i+PV) 
Dividing  through  by  e    RT      and  using  the  logarithmic  instead  of  the  exponential 

nomenclature,  we  obtain  equation  (104): 

_  /?T\ 

—  —  Jdln(z  —  AT')  (104) 

After  giving  a  kinetic  derivation  for  equation  (105),  van  Laar  follows  it  with  what 
he  terms  a  "rein  thermodynamischer"  proof.  Such  a  proof  is  of  course  impossible, 
if  by  "purely  thermodynamic"  we  are  to  understand  that  the  equation  can  be  shown 
to  be  a  necessary  consequence  of  the  two  laws  of  thermodynamics  and  nothing  else. 
In  his  papers  on  the  subject,  van  Laar  does  not  distinguish  carefully  between  purely 
thermodynamic  relations  and  relations  which  involve  additional  assumptions.  This 
makes  it  difficult  for  the  reader,  who  has  not  had  considerable  experience  in  the  use  of 
the  thermodynamic  potential,  to  appreciate  just  what  assumptions  he  is  making  and 
what  grounds  he  has  for  making  them.  Van  Laar  also  falls  into  the  error  of  attributing 
the  failure  of  the  modern  theory  of  solutions  in  the  region  of  concentrated  solutions, 
to  an  inherent  weakness  in  the  osmotic  method  which  he  condemns  severely,  at  the 
same  time  advocating  with  great  zeal  the  thermodynamic  potential  as  the  only  quantity 

60 


GENERAL,    PHYSICAL   AND   INORGANIC.  662 

of  its  thermodynamic  derivatives.  Of  these  we  will  consider  first,  the 
vapor  pressure  derivative.  The  thermodynamic  relation  connecting 
osmotic  pressure  and  vapor  pressure  is 


dr.=  \—^}*P'  (77) 

Combining  this  with  equation  (104)  so  as  to  eliminate  it  we  obtain 

Vdp  =  RTdlnN.  (in) 

RT 
If  the  vapor  can  be  regarded  as  a  perfect  gas  we  can  put  v  =  —    and 

obtain 

dln/>  =  dlnN  (112) 

which  on  integration  gives 

p  =  Pot*  («3) 

where  p0,  the  integration  constant,  is  the  vapor  pressure  of  the  pure 
solvent.  Since  the  terms  solvent  and  solute  are  quite  arbitrary,  we  can 
state  therefore  in  general  that  the  partial  vapor  pressure  of  any  constitu- 
ent of  an  "ideal  solution"  is  proportional  to  its  mol  fraction,  if  the  vapor 
obeys  Boyle's  law.  We  have  therefore  in  equation  (113)  an  excellent 
means  of  testing  our  fundamental  osmotic  equation. 

which  is  in  a  position  to  completely  solve  the  problem  (Sechs  Vortrage,  p.  19). 
This  point  of  view  is  absolutely  unjustified  and  is  doubtless  partially  responsible  for 
the  fact  that  the  many  excellent  and  valuable  features  of  this  investigator's  contribu- 
tions to  this  problem  have  not  received  from  the  chemical  world  the  consideration 
which  they  deserve.  Whether  we  should  adopt  a  system  of  thermodynamic  chemistry 
based  upon  the  entropy  function  (as  worked  out  by  Horstmann),  or  upon  one  of  the 
thermodynamic  potentials  of  Gibbs  or  Planck,  or  upon  the  "fugacity"  and  "activity" 
as  defined  by  Lewis  or  upon  the  "osmotic  pressure"  and  its  related  colligative  properties, 
is  largely  a  philosophical  question  in  which  the  personal  equation  is  an  important 
factor.  The  "best"  system  from  one  point  of  view  is  not  the  "best"  from  another, 
and  instead  of  adopting  one  of  these  systems  and  severely  condemning  the  others,  we 
should  rather  rejoice  that  the  problems  of  our  science  are  being  attacked  from  these 
different  points  of  view.  All  of  these  systems  rest  upon  the  common  ground  of  the 
first  and  second  laws  of  thermodynamics  and  any  chemical  problem  which  can  be 
solved  in  terms  of  one  of  them  can  be  solved  in  terms  of  all.  I  cannot  therefore  agree 
with  van  Laar,  that  the  so-called  "osmotic"  system  "lauft  auf  seinen  letzen  Beinen" 
and  "nach  wenige  Jahre  wird  abgereist  sein." 

Van  Laar  also  attacks  the  so-called  "gas  theory"  of  solutions,  that  is,  the  theory 
that  what  we  call  "osmotic  pressure"  is  a  real  pressure  which  exists  within  an  isolated 
solution  due  to  a  molecular  bombardment  by  the  solute  molecules.  On  this  question, 
I  sympathize  largely  with  van  Laar's  point  of  view.  His  exposition  of  the  difficulties 
in  the  way  of  such  a  theory  is  clear  and  convincing  and  I  shall  not,  therefore,  attempt 
any  further  discussion  of  the  question  at  this  time.  In  this  connection,  however,  it 
is  interesting  to  recall  the  views  held  by  Willard  Gibbs  upon  this  point.  In  speaking 
(Loc.  cit.)  of  the  osmotic  pressure  in  the  case  of  a  solution  A,  containing  a  solute,  D, 
he  says: 

"But  we  must  not  suppose  in  any  literal  sense,  that  this  difference  of  pressure 
represents  the  part  of  the  pressure  in  A  which  is  exerted  by  the  D-molecules,  for  that 
would  make  the  total  pressure  calculable  by  the  law  of  Boyle  and  Charles." 

6l 


663  FUNDAMENTAL  LAW   FOR  THEORY   OF    SOLUTIONS. 

The  next  question  which  confronts  us  is,  where  are  we  to  look  for 
solutions  whose  characteristics  approach  most  closely  those  which  we 
have  assumed  for  our  "ideal  solution,"  or  in  other  words  where  can  we 
find  solutions  for  which  we  have  reason  to  believe  that  we  know  the  mol 
fractions  of  the  constituents  in  the  solution?  Our  attention  is  naturally 
directed  towards  mixtures  of  the  so-called  "normal"  liquids  of  which 
many  examples  are  to  be  found  among  the  hydrocarbons  of  the  benzene 
series  and  their  substitution  products.  These  liquids  possess  the  property 
of  mixing  with  each  other  in  all  proportions,  the  process  of  solution  being 
accompanied  by  little  if  any  heat  effects  or  volume  changes,  such  as 
would,  in  general,  necessarily  occur,  if  the  process  of  solution  were  ac- 
companied by  chemical  reactions  such  as  solvation  or  changes  in  the  de- 
gree of  association  or  dissociation  of  any  of  the  components.  In  general 
the  physical  properties  of  these  solutions  are  additive  with  respect  to  the 
constituents.  This  behavior  is,  however,  just  what  we  should  expect 
in  the  case  of  the  "ideal  solution"  which  we  have  assumed.  We  may 
therefore  expect  to  find  experimental  confirmation  of  our  osmotic  pressure 
equation  in  the  case  of  these  solutions.  Fortunately  data  are  at  hand 
in  the  vapor  pressure  measurements  of  Zawidski  and  others.  These  data 
show  most  conclusively  that  equation  (113)  expresses  the  partial  vapor 
pressure  for  both  constituents  throughout  the  total  concentration  range 
from  zero  to  infinity  for  some  dozen  or  fifteen  different  mixtures.18  Freez- 
ing point  data  furnish  additional  confirmation  of  the  correctness  of  our 
fundamental  equation.  Van  Laar  finds,  for  example,  that  the  "freezing 
point"  curve  for  solutions  of  mercury  in  tin,  throughout  its  entire  range 
(from  t  =  232°  C.,  N'  =  o  to  i  =  — 19°,  Nf  =  0.9964),  is  satisfactorily 
represented  by  an  equation  which  rests  on  the  same  basis  as  our  funda- 
mental osmotic  pressure  equation. 

This  perfect  experimental  confirmation,  combined  with  the  light  which 
is  thrown  upon  the  subject  by  the  historical  criticism,  constitutes  a  most 
convincing  array  of  evidence  in  favor  of  the  adoption  of  the  Theory  of  the 
Ideal  Solution,  as  the  best  provisional  General  Theory  of  Solution.  Before 
turning  to  a  more  detailed  consideration  of  the  equations  of  the  Ideal 
Solution,  let  us  state  clearly  the  general  characteristics  of  such  a  solution. 

They  are  as  follows : 

18  The  mixtures  which  obey  this  vapor  pressure  law  are  as  follows: 
(i)  CO— CH8C1;  (2)  C6H14— C.H18;    (3)     C2H4Cl2--CeH,;    (3)  C,H,Br,— C.H.Br,; 
(2)    CHSOH— C^OH;    (2)    CH3COOCZH6— C.H.COOC.H.;    (2)    C.H.— C.H6CH3;    (4) 
C.H6— C6H5C1;  (4)  C.H.-C.H.Br;  (2)     C8HSCH3— C8H6CVH6;    (4)     C6H6CHS— C.H.C1; 
(4)  CFsCHi- C6HsBr;  (2)  C6HSC1— CflHsBr. 
References: 

1  Kuenen,  Z.  physik.  Chem.,  u,  38  (1893). 
1  Young,  J.  Chem.  Soc.,  81,  768;  83,  68  (1903). 

3  von  Zawidski,  Z.  physik.  Chem.,  35,  129  (1900). 

4  Linebarger,  THIS  JOURNAL,  17,  615,  690  (1895). 

This  experimental  confirmation  of  the  theory  of  the  ideal  or  "perfect"  solution 
was  pointed  out  in  a  recent  paper  by  G.  N.  Lewis  (Loc.  cit.)  who  has  computed  some 
tables  which  exhibit  in  a  very  striking  manner  the  excellent  agreement  of  equation 
(105)  with  the  experimental  data,  even  in  the  most  concentrated  solutions. 

62 


GENERAL,    PHYSICAL,   AND   INORGANIC.  664 

I.  The  number  of  molecular  species  present  is  equal  to  the  number  of 
components. 

II.  The  physical  properties  of  the  solution  are  connected  with  the  physi- 
cal properties  of  its  components  in  the  pure  state  by  the  equation 

X  =  xN  +  x'N'  +  x"N"  +  ...  (114) 

in  which  X  is  the  molecular  property  in  question  (e.  g.,  molecular  heat 
capacity,  molecular  volume,  molecular  refraction,  molecular  internal 
energy,  etc.),  x  (x',  x",  etc.)  the  molecular  property  of  a  constituent  in 
the  pure  state  and  N  (Nf,  N",  etc.)  its  mol  fraction  in  the  solution. 

III.  The  third  and  most  important  characteristic  is  that  which  describes 
the  thermodynamic  relations.     The  manner  of  stating  this  characteristic 
depends  upon  what  system  of  thermodynamics  one  chooses  to  make  use 
of.     I  shall  therefore  state  it  in  three  different  "languages." 

(a)  The  Gibbs  Thermodynamic  Potential  System. — According  to  van 
Laar  the  thermodynamic  characteristics  of  the  "ideal  solution"  are  ex- 
pressed by  the  equation 

ft  =  Ho  +  RTlnN  (115) 

in  which  /j.  is  the  molecular  thermodynamic  potential  of  a  constituent  in 
the  solution,  fio  the  molecular  thermodynamic  potential  of  the  same 
constituent  in  the  pure  state  and  N  its  mol  fraction  in  the  solution. 

(6)  The  Fugacity- Activity  System  of  Lewis. — Lewis  uses  a  system  of 
thermodynamic  chemistry  based  upon  two  quantities,  the  "fugacity" 
<j>,  and  the  "activity"  !;,  whose  relation  to  each  other  is  expressed  by  the 
equation 

<!>  =  £RT  (116) 

and  which  are  connected  with  the  thermodynamic  potential  by  the  equa- 
tion 

H  =  C  +  RTlntp  (117) 

where  C  is  a  function  of  the  temperature  only.  According  to  Lewis 
the  "perfect  solution"  is  defined  by  the  equation 

£  =  SoN  (118) 

or  what  amounts  to  the  same  thing, 

<p  =  (f>0N.  (119) 

That  van  Laar's  and  Lewis'  methods  of  describing  the  "ideal"  or  "perfect" 
solution  are  identical  is  made  evident  by  writing  equation  (i  19)  in  the  form 

RT\n<{>  =  RTlnfa  +  RTlnN,  (120) 

and  combining  it  with  equation  (117)  when  we  obtain  at  once  equation 

(US). 

(c)  The  Colligati've  Property  System  or  the  So-called  Osmotic  System. — 
According  to  this  system,  the  relation  between  the  colligative  properties 
of  the  Ideal  Solution  and  its  composition  is  expressed  by  a  set  of  equations 
which  is  composed  of  the  equation 

63 


665  FUNDAMENTAL  LAW  FOR  THEORY   OF   SOLUTIONS. 

(I04) 

and  its  thermodynamic  derivatives.17 

Having  established  fundamental  equations  for  the  Ideal  Solution,  let 
us  now  derive  a  set  of  equations  for  such  a  solution  similar  to  our  present 
equations  for  dilute  solutions,  but  free  from  any  assumptions  as  to  the 
concentration  of  the  solution.  In  deriving  such  a  set  of  equations  we  could 
start  either  with  our  osmotic  pressure  equation  (104)  or  the  vapor  pressure 
derivative  (112).  In  either  case  we  should  obtain  the  same  set  of  equa- 
tions. There  is  not  much  reason  for  choosing  one  of  these  equations 
rather  than  the  other  as  a  starting  point.  Each  possesses  certain  ad- 
vantages for  this  purpose.  In  the  following  derivations,  however,  I  shall 
start  with  the  osmotic  pressure  equation  (104)  in  each  case.  This  pro- 
cedure will  allow  of  direct  comparison  with  our  corresponding  derivations 
for  dilute  solutions  and  it  moreover  avoids  the  necessity  of  using  the 
gaseous  phase  in  the  derivation  of  a  relation  which  is  independent  of  the 
properties  of  the  vapor.  The  procedure  for  obtaining  our  set  of  equations 
is  very  simple.  In  each  instance,  it  consists  simply  in  combining  equation 
(104)  with  the  proper  purely  thermodynamic  relation  and  then  integrating 
the  result.  The  purely  thermodynamic  relations  have  all  been  obtained 
by  the  author  in  the  previous  publication3  to  which  the  reader  is  referred 
for  their  derivation.  For  convenience  in  reference  these  equations  will 
be  designated  by  the  same  numbers  as  in  the  preceding  publication.  All 
numbers  below  100  refer  to  the  previous  paper. 

3.  Vapor  Pressure. 

We  have  already  derived  this  equation  for  which  the  integrated  form 
is 

P  =  P0N  (113) 

where  p  is  the  partial  vapor  pressure  of  any  molecular  species  from  an 
ideal  solution  in  which  its  mol  fraction  is  N,  and  p0  is  its  vapor  pressure 
in  the  pure  liquid  state  at  the  same  temperature.  For  a  single  non- 
volatile solute  whose  mol  fraction  is  Nr  this  can  also  be  written  in  the  form 

A*  n' 

r  =  N'  =  -  -.  (121) 

Po  (n  +  nO 

If  in  a  mixture  of  say  two  liquids,  polymerization  of  one  or  both  con- 
stituents, or  chemical  combination  between  them  occurs,  we  can  obviously 
make  use  of  equation  (113)  to  determine  the  exact  nature  and  extent  of 
these  processes  if  we  know  the  necessary  partial  vapor  pressure  data. 
Derivatives  of  equation  (113)  for  special  cases  of  association  and  of  chemi- 
cal combination  have  been  applied  recently  with  considerable  success 

17  Regarding  the  general  characteristics  of  the  Ideal  Solution  as  stated  above,  it 
should  be  noted  that  although  in  general  the  absence  of  heat  effects  or  volume  changes 
on  mixing  two  liquids  may  be  taken  as  evidence  for  the  absence  of  accompanying 
chemical  reactions,  the  reverse  is  not  necessarily  the  case.  Heat  effects  and  volume 
changes  may  and  doubtless  do  occur  in  the  absence  of  any  chemical  reaction,  although 
in  such  a  case  the  heat  effect  will  in  the  majority  of  cases  be  of  quite  a  different  order 
of  magnitude  from  that  which  is  caused  by  a  chemical  reaction. 

64 


GENERAL,    PHYSICAL   AND   INORGANIC.  666 

by  Ikeda18  and  by  Dolezalek19  to  the  elucidation  of  the  chemical  condition 
of  several  pure  liquids  and  of  their  mixtures.  The  accumulation  of 
accurate  and  reliable  vapor  pressure  data  is  of  the  highest  importance  to 
a  clearer  and  more  complete  knowledge  of  the  nature  of  solutions.  For 
reasons  which  I  have  stated  elsewhere,21  the  vapor  pressure  equation  is 
the  relation  best  adapted  to  serve  as  a  basis  for  the  experimental  attack 
on  the  problem  of  concentrated  solutions. 

4.  The  Freezing  Point  Equation. 
If  we  combine  the  purely  thermodynamic  equation 

LF\  dTF 


(82) 

with  our  fundamental  equation 


_  RT 


\ 

Jdlntf  (104) 


so  as  to  eliminate  TT,  we  obtain  the  desired  equation2 


For  -very  dilute  solutions,  we  can  of  course  substitute  the  freezing   point 

n'  dN' 

lowering  A*/r  in  place  of  —  dTF  and  —  in  place  of  —^  and  obtain  the 

n  jv 

familiar  law  of  Raoult-van't  Hoff  for  freezing  point  lowering  in  dilute 
solution  : 


It  is  preferable,  however,  to  integrate  our  differential  equation  and 
thus  obtain  a  general  equation  for  an  ideal  solution  of  any  concentration. 
Before  doing  this  we  will  substitute  in  equation  (122) 

T0  —  Atp  =  TF,  i  —  N'  =  N  and  —  <*(  A*/r)  =  dTF 

where  A//r  is  the  freezing  point  lowering  in  centigrade  degrees  and  T0 
is  the  freezing  point  of  the  pure  solvent  on  the  absolute  scale.  This  gives 
us 

dN'  LF(i  —  N') 


In  order  to  integrate,  we  must  first  express  LF  as  a  function  of  AtF  which 
is  done  by  the  following  purely  thermodynamic  equation: 

LF  =  LFo—  ACp0A<F—  y,a(A*F)f—  V^A^)'—  ....  (85) 


18  Ikeda,  J.  Coll.  Sri.  Imp.  Univ.  Tokyo,  25,  Art.  10  (1908). 

19  Dolezalek,  Z.  physik.  Chem.,  64,  730  (1908)  ;  see  also  Moller,  Ibid.,  69,  449  (1909). 
zo  This  equation  was  obtained  by  Boldingh  (Loc.  tit.,  p.  61)  in  the  following  form: 


where  a  has  the  meaning  explained  in  note  (14).     Boldingh  integrated  his  equation 
under  the  assumption  that  LF  is  independent  of  T. 

65 


667  FUNDAMENTAL  LAW   FOR  THEORY   OF  SOLUTIONS. 

In  this  equation  Lp0  is  the  molecular  heat  of  fusion  of  the  pure  solvent 
at  its  freezing  point  T0,  ACp0  is  the  attendant  decrease  in  the  heat  capacity 
of  the  system  and  a,  /?,  etc.,  are  constants  expressing  the  dependence  of 
ACp  upon  the  temperature.  Combining  (85)  with  (125)  we  obtain  finally 
(neglecting  /?)  : 

dN'         [LFo—  &Cpo—l/,a(W](i  —  N') 


This  equation  can  now  be  integrated.  A  convenient  way  to  do  this 
is  to  integrate  into  a  power  series  in  the  desired  variable  by  applying 
McL/aurin's  theorem  directly  to  the  differential  equation,  carrying  the 
series  only  so  far  as  the  accuracy  of  the  experimental  data  warrant  for 
the  particular  case  under  consideration.  For  example,  in  the  case  of 
water  solutions  if  A/F  be  known  to  0.001°,  then  for  values  of  Atp  which 
do  not  exceed  7°,  the  terms  containing  a,  (3,  etc.,  are  negligible  and 
the  application  of  McL/aurin's  theorem  gives  us  the  equations21 


Fo  F  A  t 

v L  F~ 


AT*             — ro     I  A  j             i  /   I     "Til       .      —  — r"«  I    /  A  »    \»     I                  /          \ 

N'  —  atp —  l/,{ H I  ( A^F)a  (127) 

>-»T»      o   I  /  «  I     r-fc*nn      A      *           r                           T^  /     \           *    ' 

and 


the  remaining  terms  in  the  expansion  not  being  significant. 

If  we  desire  to  follow  a  freezing  point  curve  through  a  considerable 
range  of  temperature,  the  general  integral  of  equation  (126)  is  more  ad- 
vantageous. The  general  integral  is 


*  o 
(ACPo  +  aT0)  Afr  +  V2a  Afr«]       LFo 


Equations  of  this  general  character  have  been  derived  by  several  ob- 
servers22 and  the  corresponding  theoretical  curves  have  been  compared 
with  the  experimental  curves  for  a  number  of  systems  with  good  agreement. 
In  these  comparisons,  however,  the  constants  of  the  theoretical  equation 
have  been  evaluated  from  the  freezing  point  data  themselves,  so  that 
the  agreement  loses  a  good  deal  of  its  significance. 

5.  The  Boiling  Point  Equation. 
By  combining  the  purely  thermodynamic  equation 

21  The  application  of  equation  (127)  to  the  data  for  aqueous  solutions  and  the 
interpretation  of  the  results  obtained  have  been  discussed  by  the  author  in  a  previous 
paper  (Technology  Quarterly,   21,   370  (1908)).      This  application  was  made  on  the 
assumption  that  the  molecular  weight  of  liquid  water  is  18.     Although  the  results  ob- 
tained on  this  assumption  were  fairly  satisfactory  up  to  a  concentration  of  i  molal,  it 
is  clear  that  a  complete  study  of  the  behavior  of  aqueous  solutions  from  the  stand- 
point of  the  laws  of  the  Ideal  Solution  must  take  into  account  the  degree  of  associa- 
tion of  the  solvent.     Further  investigations  along   this  line  are  now  in  progress  in 
this  laboratory. 

22  e.  g.,  van  Laar  (Versl.  K.  Akad.  van  Wet.,  Amsterdam,  1903  and  1904;  several 
papers)  Roozeboom    ('Die  Heterogene  Gleichgewicht,"  2,  267  et.  seq.),  and  Yamamota 
(/.  Cott.  Sci.  Imp.  Univ.  Tokyo,  25,  Art.  n  (1908)). 

66 


GENERAL,,    PHYSICAL,   AND   INORGANIC.  668 

with  equation  (104)  so  as  to  eliminate  TT  we  obtain  the  desired  equation 

' 


(I30) 


which  for  very  dilute  solutions  takes  the  familiar  form 


In  order  to  integrate  the  differential  equation  (130)  we  have  only  to  ex- 
press LT,  as  a  function  of  the  temperature.  The  First  Law  of  Thermo- 
dynamics gives  us  the  rigorous  equation 

dL,  Lv      /^W^\ 

&-*-**+¥-•(-;)(&), 

by  means  of  which  we  can  calculate  the  temperature  coefficient  of  L,. 
If  the  vapor  behaves  as  a  perfect  gas  this  equation  becomes 

^  =  ACp  (133) 

dl 

and  the  methods  of  integration  of  equation  (130)  become  perfectly  analo- 
gous in  every  respect  to  those  followed  in  the  case  of  the  freezing  point 
equation  in  the  preceding  section.  It  is  not  necessary  therefore  to  discuss 
them  in  detail.  The  final  equations  have  the  same  form  as  the  corre- 
sponding ones  for  the  freezing  point  lowering. 

6.  Chemical  Equilibrium. 

Two  examples  will  be  sufficient  to  illustrate  the  method  of  derivation 
of  the  laws  which  regulate  chemical  equilibrium  in  the  ideal  solution. 
Let  the  equilibrium  be  expressed  by  the  equation  : 

oA  +  6B  +  .....  •^~>  mM  +  «N  +  ...  (134) 

(a)  The  Effect  of  Concentration.  —  The  purely  thermodynamic  equation 
for  the  effect  of  concentration  upon  chemical  equilibrium  in  a  liquid  phase 
at  constant  temperature  and  pressure  is 

—  aVfidittL  —  bVzdxB  —  .....  +  mVud^M  +  nV^dify  +  ...  ==  o  .     (300) 
According  to  equation   (104)   the  osmotic  pressure  for  each  substance 
taking  part  in  the  equilibrium  is 

Fxcfcrx  =  —  RTdlnN*.  (135) 

Combining  these  two  equations  we  obtain  the  relation 

j«  •#!'•• 

-~=*"  (136) 


where  Kv  is  a  constant.  This  expression  differs  from  the  Guldberg- 
Waage  Law  only  in  the  substitution  of  the  mol  fraction  N,  in  place  of 
the  volume  concentration  C.  Equation  (136)  was  obtained  by  Planck23  as 
early  as  1887,  and  the  reasons  for  adopting  it  in  place  of  the  Guldberg- 
Waage  form  and  for  expressing  the  composition  of  solutions  in  terms 
of  mol  fractions  instead  of  mols  per  liter  were  clearly  stated  by  him  at  the 
same  time. 

(6)  The  Effect  of  Temperature.  —  The  purely  thermodynamic  relation  is 

OxdT 
—  .  .  .    +  ml/Mrf~M  +  nV^dr^  +  .  .  .  =  .    (380) 


Planck,  Wied.  Ann.,  32,  489  (1887). 

6? 


669  FUNDAMENTAL  LAW   FOR  THEORY   OF   SOLUTIONS. 

Combining  this  with  equations  (136)  and  (135)  and  introducing  the  First 
Law  of  Thermodynamics  we  obtain  the  equation 

d^Kff  =   U_ 
dT         RT* 

which  is  identical  with  the  van't  Hoff  Law,  with  the  substitution  of  Kjy 
in  place  of  the  Guldberg-Waage  constant  KC-  In  general  it  may  be 
stated  that  the  laws  for  chemical  equilibrium  in  an  ideal  solution  may 
be  obtained  from  our  present  dilute  solution  laws  by  substituting  mol 
fractions  in  place  of  volume  concentrations.  This  applies  also  to  hetero- 
geneous equilibrium.  The  Solubility  Product  Law,  for  example,  for  a 
saturated  solution  of  the  solute  BC  which  dissociates  into  B  and  C  be- 
comes24 

WB'NC  =  const.  =  KS.  (138) 

7.  Concluding  Discussion. 

Lest  any  one  from  the  perusal  of  the  foregoing  pages  should  gain  the 
impression  that  the  problem  of  a  satisfactory  general  theory  of  solutions 
may  be  regarded  as  completely  solved,  it  will  be  well  to  examine  for  a 
moment,  in  a  general  way,  the  characteristics  of  the  Theory  of  the  Ideal 
Solution  with  respect  to  its  advantages  and  disadvantages  when  regarded 
as  the  basis  for  a  general  theory  of  solutions.  When  compared  with  the 
Theory  of  Dilute  Solutions  we  must  acknowledge  that  it  constitutes  a 
distinct  and  decided  step  forward.  One  requirement  of  a  satisfactory 
general  theory  of  solutions  is  that  it  shall  represent  the  facts  throughout 
the  whole  range  of  concentrations  for  some  type  of  solution,  at  least. 
This  requirement  is  fulfilled  by  the  Theory  of  the  Ideal  Solution  and  we 
may  feel  considerable  certainty  that  any  deviation  from  the  requirements 
of  this  theory,  in  a  given  case,  is  due  to  physical  or  chemical  causes  and 
capable  of  a  physical  or  chemical  explanation  and  is  not  simply  the  result 
of  attempting  to  apply  a  set  of  incomplete  laws  which  do  not  and  could 
not  be  expected  to  hold  for  any  kind  of  a  concentrated  solution  no  matter 
how  simple  its  character. 

The  success  of  the  Theory  of  the  Ideal  Solution  as  an  instrument  for 
throwing  light  upon  the  processes  occurring  in  solutions  has  already  been 
demonstrated  in  several  instances.  In  the  case  of  several  solutions  which 
apparently  exhibit  a  behavior  contrary  to  the  requirements  of  the  Theory, 
Dolezalek19  has  shown  that  perfect  agreement  between  theory  and  ex- 
periment exist  if  the  assumption  be  made  that  a  simple  compound  is 
formed  between  the  two  constituents  or  that  one  of  them  is  partially 
associated.  In  the  case  of  acetone  and  chloroform  for  example,  the  as- 
sumption of  a  single  compound,  CHC13  (CH3)2CO,  and  the  introduction 
of  the  corresponding  equilibrium  constant  into  the  equations  sufficed  to 
produce  complete  agreement  between  theory  and  experiment.  It  is  true 
that  the  value  of  the  constant  was  computed  from  the  vapor  pressure 
data  themselves,  but  in  a  recent  paper19  Holier  has  shown  that  the  values 
of  such  constants  may  be  obtained  independently  of  the  vapor  pressure 
data  of  the  solution  under  consideration  and  that  they  therefore  possess 
24  This  is  obtained  by  combining  equations  (51)  and  (104).  It  does  not  involve 
the  Mass  Action  Law  [i.  e.,  equation  (136)],  which  is  usually  assumed  as  the  basis  for 
the  derivation  of  the  Solubility  Product  Law.  This  point,  which  was  brought  out  in 
the  previous  paper,  has  been  overlooked  in  all  of  the  textbooks  of  physical  chemistry, 
although  it  was  explained  clearly  by  Planck  as  early  as  1887  (Loc.  cit.). 

68 


GENERAL,    PHYSICAL   AND   INORGANIC.  670 

the  physical  significance  ascribed  to  them  and  are  not  simply  empirical 
constants  of  an  interpolation  formula. 

In  all  the  cases  studied  by  Dolezalek  he  found  that  agreement  between 
experiment  and  theory  is  produced  if  the  assumption  be  made  that  what 
appears  to  be  a  deviation  from  the  theory  is  simply  due  to  the  fact  that 
the  numbers  assumed  as  the  mol  fractions  of  the  two  constituents 
in  the  solution  are  incorrect  and  that  when  the  proper  mol  frac- 
tions are  used,  the  apparent  discrepancy  disappears.  If  we  were 
justified  in  assuming  that  all  solutions  are  really  ideal  solutions  and 
that  what  appear  to  be  exceptions  are  merely  due  to  our  inadequate 
knowledge  of  the  number  and  kind  of  the  various  molecular  species  present 
and  their  respective  mol  fractions,  then  the  Theory  of  the  Ideal  Solution 
would  constitute  a  general  theory  including  all  solutions  and  all  con- 
centrations and  would  enable  us  to  ascertain  just  what  occurs  chemically, 
when  the  solution  is  formed  out  of  its  constituents.  Unfortunately  such 
is  not  the  case,  for  it  can  be  easily  shown  mathematically  that  if  certain 
liquids  form  an  ideal  solution  with  one  another  they  must  be  miscible 
in  all  proportions.  The  solutions  in  a  system  composed  of  two  or  more 
liquid  phases  in  equilibrium  with  one  another  cannot  therefore  be  governed 
to  the  laws  of  the  Ideal  Solution.  Moreover,  these  exceptions  are  not 
merely  apparent  but  are  real  and  cannot  be  explained  on  the  grounds  of 
association,  dissociation  or  chemical  combination.  The  explanation 
must  be  looked  for  in  a  radical  difference  in  the  physical  nature  of  the 
medium. 

To  illustrate  by  an  extreme  case,  let  us  consider  a  system  composed  of 
a  solution  of  benzene  in  mercury  and  a  solution  of  mercury  in  benzene, 
both  solutions  in  equilibrium  with  each  other.  The  vapor  pressure  of 
benzene  from  the  mercury  layer  is  equal  to  its  vapor  pressure  from  the 
benzene  layer  and  yet  the  mol  fraction  of  benzene  in  the  mercury  layer 
is  probably  so  small  that  we  could  not  detect  it  by  any  analytical  means, 
while  in  the  benzene  layer  it  is  equal  to  i ,  within  the  limits  of  our  ability  to 
measure  it.  The  equality  of  the  vapor  pressure  from  the  two  layers  can 
only  be  due,  therefore,  to  the  fact  that  the  nature  of  the  medium  between 
the  molecules  of  mercury  is  such  that  the  benzene  molecules  can  penetrate 
it  only  with  the  greatest  difficulty.  This  effect  of  the  physical  nature  of 
the  medium  is  therefore  one  which  must  be  taken  account  of  in  all  applica- 
tions of  the  Theory  of  the  Ideal  Solution.  In  order  that  the  laws  of  the 
Ideal  Solution  shall  apply,  the  nature  of  the  medium  or  the  field  of  force 
in  which  the  molecules  find  themselves  in  the  solution  must  not  be  -very 
different  from  that  of  the  pure  liquid  itself.  Although  this  restricts  some- 
what the  sphere  of  usefulness  of  the  theory,  there  still  remain  a  large 
number  of  cases  where  it  should  prove  of  the  greatest  value  in  the  elucida- 
tion of  the  chemical  nature  of  solutions.  Even  in  cases  where  the  theory 
cannot  be  extended  over  all  concentrations  because  of  a  consequent 
radical  change  in  the  physical  nature  of  the  medium,  we  may  still  hope 
to  obtain  valuable  results  with  its  aid  in  solutions  of  moderate  concen- 
trations. At  all  events,  I  believe  that  the  Theory  of  the  Ideal  Solution 
is  the  one  which  should  be  adopted  as  the  basis  for  reference,  classification 
an  interpretation  of  the  experimental  data  on  solutions  in  place  of  our 
present  Theory  of  the  Infinitely  Dilute  Solution  which  is  only  a  special, 
though  very  important,  case  of  the  former  theory. 

URBANA,  ILLINOIS,  Feb.  i,  1910. 

69 


A  REVIEW  OF   SOME  RECENT   INVESTIGATIONS  IN  THE  QUIN- 

AZOLINE  GROUP.1 

BY  MARSTON  TAYLOR  BOGERT. 
Received  March  31,  1910. 

For  several  years  past,  the  Organic  Laboratory  of  Columbia  Univer- 
sity has  been  engaged  in  the  synthesis  and  study  of  compounds  belonging 
to  that  group  of  organic  heterocycles  known  as  quinazolines  or  phen- 
miazines. 

To  us,  the  work  has  been  most  interesting  and  enjoyable.  The  com- 
pounds obtained  have  been  generally  crystalline  solids,  quite  readily 
purified,  stable,  and  very  satisfactory  to  work  with. 

Our  investigations  have  included — A.  Quinazolines,  B.  Thioquinazo- 
lines,  and  C.  Naphthotetrazines  of  quinazoline  structure : 

N  N  N 


N-  NN 


(Quinazoline)  (Thioquinazoline)  (1,3,7,9-Naphthotetrazine) 

Incidentally,  a  great  many  new  preparatory,  intermediate  and  sub- 
sidiary products  have  been  obtained.  From  the  standpoint  of  new  sub- 
stances, the  field  has  been  an  unusually  fruitful  one. 

It  is,  therefore,  not  only  an  honor  but  also  a  pleasure  to  present  on 
this  occasion  a  brief  synopsis  of  the  major  lines  of  the  work  to  date. 

A.   Quinazolines. 

Colby  and  Dodge,2  as  the  result  of  their  investigations  of  the  inter- 
action of  nitriles  and  organic  acids,  under  conditions  of  heat  and  pres- 
sure, came  to  the  following  conclusions: 

I.  Fatty  nitriles  and  aromatic  acids  give  fatty  acids  and  aromatic 
nitriles. 

II.  Aromatic  nitriles  and  fatty  acids  give  mixed  secondary  amides. 

III.  Aromatic  nitriles  and  aromatic  acids  give  secondary  amides,  un- 
less the  temperature  is  very  high,  when  the  nitrile  of  the  higher  radical 
may  form. 

Mathews,3  in  continuation  of  this  work,  heated  acetonitrile  and  an- 
thranilic  acid  together  under  pressure,  hoping  thereby  to  obtain  the 

1  Presented  at  the  Twentieth  Anniversary  Celebration  of  Clark  University,  Wor- 
cester, Mass.,  Sept.  14,  1909. 

2  Am.  Chem.  J  .,  13,  i  (1891). 

3  THIS  JOURNAL,  20,  654  (1898). 

70 


RECENT   INVESTIGATIONS   IN  THE   QUINAZOLINE   GROUP.  785 

anthranilic  nitrile.  On  examining  the  contents  of  the  tube,  he  found 
not  the  nitrile  desired  but  a  colorless  crystalline  compound,  melting 
at  232°  (uncor.),  which  was  not  identified  at  the  time. 

Later,  Bogert  and  Gotthelf1  made  a  more  careful  study  of  this  reac- 
tion and  found  that  the  crystalline  substance  melting  at  232°  was  identical 
with  the  2-methyl-4-ketodihydroquinazoline  first  described  by  Weddige,2 
and  later  obtained  by  Bischler  and  Burkart,3  Bischler  and  Lang,4  and 
Niementovskii.5  By  varying  the  nitrile,  they  obtained  other  quinazolines 
of  analogous  structure. 

Continuing  this  work,  Gotthelf8  heated  anthranilic  acid  under  pressure 
with  a: 

IV.  Fatty  nitrile  alone  (using  aceto-,  propio-,  w-butyro-,  t-valero-  and 
i-capronitriles). 

V.  Fatty  nitrile  and   the  corresponding  fatty  acid   (acetonitrile  and 
acetic  acid,  propionitrile  and  propionic  acid,  etc.). 

VI.  Fatty  nitrile  and  a  higher  fatty  acid  (acetonitrile  and  propionic 
acid,  n-butyronitrile  and  capric  acid,  etc.). 

VII.  Fatty  nitrile   and  a  lower  fatty  acid   (isocapronitrile   and  pro- 
pionic acid,  etc.). 

VIII.  Fatty  nitrile  and   the  corresponding  acid  anhydride   (propioni- 
trile and  propionic  anhydride,  valeronitrile  and  valeric  anhydride,  etc.). 

IX.  Fatty  nitrile   and   higher  acid  anhydride    (acetonitrile   and   pro- 
pionic anhydride,  etc.). 

X.  Fatty  nitrile  and  lower  acid  anhydride   (acetonitrile  and  formic 
acid,  etc.). 

In  considering  case  IV,  Bogert  and  Gotthelf  at  the  time  thought  it 
probable  that  the  production  of  a  quinazoline  was  due  to  the  formation 
of  an  intermediate  secondary  amide. 


,NH,  X»  X    =          3 

C.H4<  +  CH8CN  =  C.A4<          — fi1        =C6H4<  |         +  H,O 

VOOH  XCONHCCH3  XCO  .  NH 

just  as  acetonitrile  and  acetic  acid  when  heated  under  pressure  give 
diacetoamide.7 

One  objection  to  this  explanation  of  the  course  of  the  reaction  lies 
in  the  fact  that  it  involves  a  lactam  condensation,  whereas  Weddige's 
investigations  in  this  very  field  have  made  it  quite  clear  that  these  con- 
densations follow  preferably  the  lactim  course.  If  the  intermediate 
secondary  amide  assumed  by  us  passes  directly  into  the  quinazoline  by 
loss  of  water,  two  different  quinazolines  should  result  according  to  whether 
the  condensation  is  of  lactam  or  lactim  type : 


y 

C6H4< 
N 


O 


+HtO 


CONHCCH,  CO  .  NH 

(a) 

1  THIS  JOURNAL,  22,  129  (1900). 

2  J.  prakt.  Chem.,  [2]  31,  124  (1885). 

3  Ber.,  26,   1350   (1893). 

4  Ibid.,  28,  282  (1895). 

8  /.  prakt.  Chem.,  [2]  51,  564  (1895)  and  Ber.,  29,  1360  (1896). 

•THIS  JOURNAL,.,  23,  6n  (1901). 

7  Kekuld,  Lehrbuch  (ist  ed.),  i,  574;  Gautier,  Ztschr.  Chem.,  1869,  127. 

71 


786  ORGANIC   AND   BIOLOGICAL. 


6H4<( 


•NH  H  OH  .NH.CCH, 

+  H,0 


CON:CCH3  CO.N 

(*) 
As  a  matter  of  fact,  the  product  obtained  by  us  is  identical  with  (a). 

Another  objection  is  that  it  is  not  in  harmony  with  the  conclusions 
of  Colby  and  Dodge1  cited  above.  According  to  their  experiments, 
the  first  products  of  the  action  of  a  fatty  nitrile  upon  an  aromatic  acid 
at  high  temperature  and  pressure  are  the  aromatic  nitrile  and  the  fatty 
acid,  which  may  and  often  do  subsequently  combine  to  a  mixed  secondary 
amide.  That  the  secondary  amide  is  not  the  first  product  seems  established 
by  their  results,  for  in  no  case  where  a  fatty  nitrile  acted  upon  an  aro- 
matic acid  was  the  secondary  amide  found  unaccompanied  by  aromatic 
nitrile,  while  in  many  cases  aromatic  nitrile  and  fatty  acids  were  found 
unaccompanied  by  any  secondary  amide.  Thus,  acetonitrile  and  benzoic 
acid  at  220°  gave  no  acetobenzamide,  but  only  benzonitrile  and  acetic 
acid,  whereas  when  the  latter  two  were  heated  together  at  220°,  only 
acetobenzamide  was  formed. 

It  therefore  seems  probable  that  the  first  phase  of  the  reaction  be- 
tween anthranilic  acid  and  a  fatty  nitrile  is  as  follows: 
HH,  /NH, 

+  RCN  =  ceHK        +  R.COOH 

COOH  \CN 

As  aniline  when  heated  to  sufficiently  high  temperatures  with  fatty 
acids  yields  the  corresponding  anilides,2  the  second  phase  of  the  reaction 
is  probably 

.NH,  .NH.COR 

C6H4<  +  R.COOH  =  C9H4<  +  H,0. 


/ 
4V 

\ 


As  the  ease  with  which  this  acylation  takes  place  decreases  with  in- 
crease in  the  molecular  weight  of  the  fatty  acid,  the  higher  nitriles  should 
give  smaller  yields  of  the  quinazoline,  and  this  was  found  to  be  the  case. 
The  yield  with  propionitrile,  for  example,  was  22.5  per  cent.,  while  with 
valeronitrile  it  was  only  5  per  cent,  of  the  theoretical. 

The  acylanthranilic  nitrile  may  then  pass  into  the  quinazoline  by  either 
of  the  following  reactions: 

.NH.COR  xNH.COR  ,K  =  CR 

C6H4<  +  H80=C6H,<  =  C6H4<  I       +HkO 

XCN  \CONH,  \CO  .  NH 

or 

xNH.COR  XNH.COR  /N  =  CR 

C6H4<  +  R.COOH  =  C6H4<  =C6H4<  |      +  R.COOH. 

\CN  \CONHCOR  XCO  .  NH 

That  a  simple  molecular  rearrangement  of  the  acylanthranilic  nitrile 
occurs, 

xNH.COR  N  =  CR 


CN  co  .  NH 

seems  unlikely,  for  the  reason  that  when  acetoanthranilic  nitrile  was 
heated  for  some  time  above  its  melting  point,  or  when  its  solution  in 
dry  toluene  was  heated  to  high  temperatures  in  sealed  tubes,  no  change 

1  Loc.  cit. 

2  Williams,  Ann.,  131,  288;  Pebal,  Ibid.,  91,  152. 

72 


. 

RECENT   INVESTIGATIONS   IN   THE   QUINAZOUNE   GROUP.  787 

whatever  occurred.1  Moisture  was,  of  course,  rigidly  excluded  in  these 
experiments,  since  a  small  amount  of  water,  by  successive  addition  and 
splitting  off,  would  suffice  to  convert  an  indefinite  amount  of  the  nitrile 
to  the  quinazoline. 

In  further  support  of  the  assumption  that  the  acylanthranilic  nitrile 
is  an  intermediate  product,  are  the  following  facts:  (i)  Acetanilide  is 
found  as  a  by-product  in  the  tubes.2  (2)  The  presence  of  a  small  amount 
of  acetic  anhydride  greatly  increases  the  yield  of  quinazoline.  (3)  The 
same  quinazoline  results  when  acetoanthranilic  acid  is  heated  in  a  sealed 
tube  with  acetonitrile  as  when  anthranilic  acid  itself  is  used.3  (4)  Aceto- 
anthranilic nitrile  on  partial  hydrolysis  changes  immediately  to  the 
quinazoline.4 

The  by-products  observed  in  the  experiments  were  carbon  dioxide, 
aniline,  anilides,  amides  and  ammonia.  Of  these,  carbon  dioxide  and  ani- 
line are  normal  decomposition  products  of  anthranilic  acid  at  high  tem- 
peratures. Partial  hydrolysis  of  the  nitrile  accounts  for  the  presence  of 
amide.  Aniline  acting  on  the  latter,5  or  upon  the  fatty  acid  present, 
yields  the  anilide,  the  by-product  in  the  former  case  being  ammonia. 

In  those  cases  (V,  VI  and  VII)  where  the  anthranilic  acid  was  heated 
with  both  the  fatty  nitrile  and  the  fatty  acid,  the  results  are  confusing 
and  the  interpretation  obscure.  Quinazolines  were  formed,  but  the 
course  of  the  reactions  is  not  clear  and  additional  work  is  needed  before 
any  satisfactory  conclusions  can  be  reached. 

When  an  acid  anhydride  was  added  to  the  tubes  containing  the  an- 
thranilic acid  and  fatty  nitrile  (VIII,  IX  and  X),  the  anhydride  used 
determined  the  quinazoline  formed  in  practically  every  case.  In  these 
experiments,  the  reaction  is  therefore  probably  as  follows: 

yNH,  .NH.COR 

C6H,<  +  O(CO.R)2  =  C6H4<  +  R.COOH 

XCOOH  XCOOH 

/NH.COR  /NH.COR 

C6H/  +  R'CN  =  C6H/ 

XCOOH  XCONHCOR', 

the  latter  then~condensing  in  either  of  the  following  ways: 


N:C 


X  ,N 


CONH 


OH 
COR 


).NH 


+  R'COOH     (a) 


C6H/ 


NHCOR 


,N  =  CR' 


R' 


=  C8H4/  |       +  R.COOH 

VO  .  NH 


The  nitrile  was  used  with  the  corresponding  acid  anhydride  (VIII), 
with  a  higher  acid  anhydride  (IX),  and  with  a  lower  anhydride  (X).  Of 
these,  types  VIII  and  IX  invariably  yielded  pure  quinazolines  according 
to  reaction  (a)  above.  Only  when  a  lower  anhydride  was  used  with  the 

1  Bogert  and  Hand,  THIS  JOURNAL,  24,  1034  (1902). 

2  Bogert  and  Gotthelf,  Ibid.,  22,  528  (1900). 

3  Bogert  and  Gotthelf,  Loc.  cit. 

4  Bogert  and  Hand,  Loc.  cit. 

6  Kelbe,  Ber.,  16,  1200  (1883). 

73 


788  ORGANIC  AND   BIOLOGICAL. 

nitrile  (X),  were  products  encountered  which  were  mixtures  of  quinazo- 
lines. 

Of  these  different  sealed-tube  reactions,  much  the  best  was  that  in 
which  the  anthranilic  acid  was  heated  with  the  fatty  nitrile  and  the 
corresponding  acid  anhydride  (VIII).  The  yield  by  this  process  was 
fair  (30  to  50  per  cent,  of  the  theory)  and,  unless  the  heating  was  too 
high,  the  tube  contents  were  invariably  light-colored  and  crystalline. 

In  the  foregoing,  it  is  assumed  that  the  secondary  amide  is  an  inter- 
mediate product  in  the  formation  of  the  quinazoline.  Such  an  amide, 
R.CO.NH.CO.R',  being  symmetrical,  should  be  producible  either  from 
R.COOH  and  R'CN,  or  from  R'COOH  and  RCN.  In  other  words, 
since  the  formation  of  the  — CO.NH.CO —  group  is  due  solely  to  the 
combination  of  the  CN  and  COOH,  it  should  make  no  difference  which 
radical  carries  the  CN  and  which  the  COOH.  The  same  secondary  amide 
and,  therefore,  the  same  quinazoline,  should  result  whether  the  acylan- 
thranilic  acid  is  heated  with  the  fatty  nitrile,  or  the  acylanthranilic  nitrile 
with  the  fatty  acid  (or  its  anhydride).  On  testing  this  practically,1  such 
was  indeed  found  to  be  the  case,  and  a  number  of  quinazolines  were 
thus  obtained  from  the  acylanthranilic  nitriles  by  heating  them  in  sealed 
tubes  with  the  fatty  acid  or,  better,  its  anhydride. 

In  experimenting  with  these  acylanthranilic  nitriles,  a  method  of 
converting  them  into  the  quinazolines,  far  superior  to  any  of  the  methods 
described  above,  was  discovered.  It  consists  in  digesting  the  acylan- 
thranilic nitrile  for  a  few  minutes  with  a  warm  alkaline  dioxide  solution, 
and  is  really  a  beautiful  method,  being  very  rapid,  simplicity  itself  in 
execution,  and  giving  large  yields  of  practically  pure  quinazolines.  It 
depends  upon  the  hydrolysis  of  the  nitrile  to  the  amide,  the  acylanthranil- 
amide  then  condensing  to  the  quinazoline,  as  shown  by  Weddige.2 

In  those  cases  where  the  o-amino  acid  is  best  obtained  from  its  nitrile 
by  saponification,  it  is  convenient  to  be  able  to  pass  direct  from  the 
nitrile  to  the  quinazoline.  Thus,  homoanthranilic  nitrile  is  readily 
prepared  from  ra-nitro-/>-toluidine,  through  w-nitro-/>-toluonitrile,  and 
from  the  acyl  derivatives  of  this  homoanthranilic  nitrile  and  an  alkaline 
dioxide  solution  (hydrogen  dioxide  solution  made  alkaline  with  sodium 
hydroxide),  the  7-methyl-4-quinazolones  were  prepared.3 

By  a  number  of  different  processes,  including  those  already  mentioned, 
starting  with  brominated  anthranilic  acdis,  bromoquinazolines  were  pre- 
pared.4 

Our  attention  was  next  turned  to  the  nitroquinazolines,  and  many 
were  made  from  nitroanthranilic  acids  by  the  methods  already  described, 
and  also  by  heating  the  ammonium  salt  of  the  nitroanthranilic  acid 
with  formamide,5  by  the  direct  action  of  heat  on  the  ammonium  salts 
of  nitroacylanthranilic  acids,6  and  by  the  action  of  primary  amines  on 
nitroacetoanthranils.7  The  last  is  a  very  fine  method  indeed,  and  one 
we  have  developed  quite  extensively. 

1  Bogert  and  Hand,  THIS  JOURNAL,  24,  1031  (1902). 

2  J.  prakt.  Chem.,  [2]  31,  124  (1885);  36,  141  (1887). 

3  Bogert  and  Hoffman,  THIS  JOURNAL,  27,  1293  (1905). 

4  Bogert  and  Hand,  Ibid.,  25,  943  (1903);  28,  94  (1906). 

5  Niementovskii,  /.  prakt.  Chem.,  [2]  51,  564  (1895). 
8  Bischler  and  Burkart,  Ber.,  26,  1349  (1893). 

7  Anschiitz,  Schmidt  and  Griffenberg,  Ber.,  35,  3480  (1902). 

74 


RECENT   INVESTIGATIONS   IN  THE   QUINAZOLINE   GROUP.  789 

By  these  various  methods,  we  prepared  5-nitro-,1  6-nitro-2,  and  y-nitro- 
4-quinazolones.3  Of  the  four  possible  types  of  benzoylnitroquinazolines, 
representatives  of  the  6-nitro,4  and  8-nitro,5  were  already  known.  The 
preparation  of  the  5-and  y-nitro  derivatives  completed  the  series. 

Reduction  of  the  nitroquinazolines  yielded  the  corresponding  benzoyl- 
aminoquinazolines,6  in  which,  as  might  have  been  expected,  the  amino 
group  shows  the  usual  aniline  reactions. 

Aminoquinazolines  with  the  amino  group  on  the  miazine  side  of  the 
nucleus  were  produced  by  condensing  simple  or  substituted  acylanthranils 
with  primary  hydrazines,7 

N.COR  /N  =  CR 

H,N.NHR'  =  C6H4<  |  +  HSO. 

\CO  .  N.NHR' 

With  hydrazine  itself,  it  was  also  found  possible  to  condense  two  mol- 
ecules of  the  anthranil  with  one  of  the  hydrazine,  thereby  giving  3,3'- 
diquinazolonyls, 

=  Cr    RC  =  N, 


.  N N.  CC 

The  same  result  can  be  accomplished,  though  less  satisfactorily,  by  con- 
densing the  3-aminoquinazoline  with  a  second  molecule  of  the  anthranil. 
The  di-quinazolonyls  so  far  isolated  are  all  very  difficultly  soluble  and 
inert. 

The  3-aminoquinazolines  proved  interesting  because  of  their  unsym- 
metrical  secondary  hydrazine  structure,  >N.NH2.  In  the  main,  their 
properties  coincide  with  those  of  other  N-amino  heterocyclic  compounds. 
Thus,  nitrous  acid  does  not  diazotize  the  amino  group,  but  replaces  it 
by  hydrogen;  with  diacetosuccinic  esters,  they  often  yield  pyrrole  de- 
rivatives;8 with  aromatic  nitroso  bodies,  they  do  not  give  azo  compounds; 
nor  are  they  oxidized  to  tetrazones  by  mercuric  oxide.  On  the  other 
hand,  they  do  not  usually  condense  with  ketones,  while  they  do  occasion- 
ally yield  phenyluramino  derivatives  with  phenyl  isocyanate.9  In  the 
elimination  of  the  N-amino  group  by  the  action  of  nitrous  acid,  there 
must  be  some  unstable  intermediate  product  formed,  for  if  immediately 
after  the  addition  of  the  nitrous  acid  the  mixture  be  poured  into  an  alkaline 
solution  of  alpha-  or  beta-naphthol,  dyestuffs  are  formed  of  considerable 
tinctorial  power,  the  structure  of  which  has  not  been  elucidated. 

Further  experimentation  with   the   acylanthranils  showed   that   they 

1  Bogert  and  Chambers,  THIS  JOURNAL,  27,  649  (1905);  Bogert  and  Sell,  Ibid., 
27»  1305  (1905)  and  29,  532  (1907). 

2  Bogert  and  Cooke,  Ibid.,  28,  1449  (1906). 

3  Bogert  and  Steiner,  Ibid.,  27,  1327  (1905);  Bogert  and  Sell,  Ibid.,  29,  532  (1907); 
Bogert  and  Klaber,  Ibid.,  30,  807  (1908). 

4  Dehoff,  /.  prakt.  Chem.,  [2]  42,  347  (1890);  Thieme,  Ibid.,  43,  441  (1891). 

5  Zacharias,  Ibid.,  43,  441  (1891). 

8  Bogert  and  Chambers,  THIS  JOURNAL,  28,  207  (1906);  Bogert  and  Klaber,  Ibid., 
30,  807  (1908). 

7  Bogert  and  Sell,  Ibid.,  28,  884  (1906);  Bogert  and  Cook,  lloc.  cit.;  Bogert  and 
Klaber,  Loc.  cit. 

8  Billow,  Ber.,  35,  4312  (1902);  39,  2621  and  3372  (1906). 

9  Bogert  and  Gortner,  THIS  JOURNAL,  31,  943  (1909). 

75 


790  ORGANIC   AND    BIOLOGICAL. 

could  also  be  condensed  with  amino  nitrils  or  amino  esters  to  the  cor- 
responding quinazolines.1 

The  ease  with  which  acylanthranils  condense  with  primary  amines  to 
crystalline  quinazolines  suggests  the  utilization  of  this  reaction  for  the 
separation  and  identification  of  easily  soluble  or  sirupy  amines  difficult 
to  handle  otherwise. 

The  same  reaction  was  employed  for  the  preparation  of  quinazoline 
carboxylic  acids  from  acylanthranil  carboxylic  acids,2 

XN.COR  ,N  =  CR 

HOOC.CeH3<    |  +  zR'NH,  =  R^NH3OOC.C4H3<  |       +  H,O. 

NCO  \CO  .  NR' 

These  quinazoline  benzoylcarboxylic  acids  are  colorless  crystalline 
solids,  melting  with  decomposition  above  300°,  more  or  less  soluble  in 
alcohol,  but  very  difficultly  soluble  in  other  neutral  organic  solvents. 

From  the  oxalyl  anthranils,  quinazolinecarboxylic  acids  were  pre- 
pared carrying  the  carboxyl  group  on  the  miazine  side  of  the  nucleus,3 

.N.COCOOR  .N  =  C.COOR 

C6H/  |  +  R'NH,  ==  C6H4<  |  +  H,0. 

NCO  NCO  .  NR' 

The  particular  quinazolines  described  in  the  foregoing  are  for  the  most 
part  of  the  type  designated  as  4-ketodihydroquinazolines  or,  more  simply, 
4-quinazolone  s, 


O 
(4) 

When  there  is  an  H  at  position  3  instead  of  a  radical,  there  arises  the 
possibility  of  keto-enolic  tautomerism, 

.N  =  CR  XN  ==  CR 

C,H/  |       ^±  C6H/  |     . 

XCO.NH  \C(OH):N 

(4-Quinazolone)         (4-Hydroxyquinazoline) 

All  those  4-quinazolones  (4-hydroxyquinazolines)  which  carry  a  hydro- 
gen at  position  3  are  easily  soluble  in  aqueous  solutions  of  the  caustic 
alkalies  and  re-precipitable  from  such  solutions  by  carbon  dioxide  or 
acetic  acid.  When  these  alkali  salts  are  treated  with  alkyl  halides,  the 
3-(JV)alkyl  derivative  is  the  chief  product.4  The  nitro  derivatives  furnish 
an  apparent  exception  to  this,  in  that  the  product  with  the  higher  alkyl 
halides  is  reported  as  chiefly  the  oxygen  ether  (i.  e.,  the  4-(<9)alkyl,  or 
-OR  compound).5  We  are  somewhat  skeptical,  however,  of  the  accuracy 
of  these  results  and  feel  that  they  should  not  be  fully  accepted  until  the 
pure  oxygen  ethers  have  been  prepared  by  other  processes  and  the  two 

1  Bogert  and  Klaber,  Loc.  cit. 

2  Bogert,  Wiggin  and  Sinclair,  THIS  JOURNAL,  29,  82  (1907);  Bogert  and  Jouard, 
Ibid.,  31,  489  (1909). 

3  Bogert  and  Gortner,  Ibid.,  32,  119  (1910). 

4  Bogert  and  May,  Ibid.,  31,  507  (1909). 

5  Bogert  and  Seil,  Ibid.,  29,  517  (1907). 

76 


RECENT   INVESTIGATIONS   IN   THE   QUINAZOLINE    GROUP.  79 1 

products  compared.  One  reason  for  this  skepticism  on  our  part  is  that 
certain  of  these  suppositious  oxygen  ethers  could  not  be  hydrolyzed  with 
concentrated  mineral  acids  (hydrochloric),  a  result  contrary  to  our  ex- 
perience and  to  that  of  others  working  with  true  oxygen  ethers. 

Pure  3-(A^)alkyl  derivatives  are  easily  obtained  by  the  acylanthranil 
reaction  already  described.  For  the  isomeric  4-OR  derivatives,  the 
best  method  appears  to  be  the  treatment  of  the  4-chloroquinazolines 
with  sodium  alcoholates.1  In  the  case  of  the  simple  alkyl  derivatives 
of  unsubstituted  4-quinazolones  (4-hydroxyquinazolines),  the  (3)-NR 
compounds  are  colorless,  odorless  solids,  quite  soluble  in  water,  gen- 
erally very  difficultly  volatile  with  steam,  of  higher  melting  point  than 
the  4-OR  isomers,  and  are  not  hydrolyzed  by  strong  hydrochloric  acid. 
On  the  other  hand,  the  4-OR  compounds  are  oily  liquids  or  low-melting 
solids,  usually  of  pleasant  odor,  readily  volatile  with  steam,  less  soluble 
in  water  but  more  soluble  in  hydrochloric  acid  than  the  NR  isomers, 
and  are  readily  hydrolyzed  by  mineral  acids  to  the  hydroxyquinazoline 
(4-quinazolone)  again.  Some  of  the  lower  ones  can  even  be  distilled 
undecomposed  at  ordinary  pressure. 

In  the  preparation  of  the  4-chloroquinazolines  from  the  4-hydroxy- 
quinazolines (4-quinazolones),1  a  methyl  or  ethyl  group  in  position  2 
exerts  a  peculiar  influence  upon  the  course  of  the  reaction  with  phos- 
phorus halides  or  similar  halogenating  reagents.  In  all  such  cases,  it 
was  found  impossible  to  replace  the  OH  at  4  by  chlorine  without  simul- 
taneously introducing  three  chlorine  atoms  in  the  benzene  part  of  the 
nucleus.  Even  when  2,3-dimethyl-4-quinazolone  was  heated  with  phos- 
phorus penta-  and  oxychlorides,2  the  3-methyl  group  was  split  off,  a  Cl 
attached  itself  at  4,  but  again  three  Cl's  entered  the  benzene  nucleus. 

Our  investigations  in  this  4-quinazolone  group  have  led  to  the  syn- 
thesis and  study  of  derivatives  carrying  the  following  substitutions: 

1.  At  position,  2-,  methyl,  ethyl,  normal  and  isopropyl,  isobutyl,  isoamyl, 
phenyl,  m-  and  />-nitrophenyl,  benzyl,  p-to\yl,  COOH,  and  various  com- 
plex radicals  and  residues. 

2.  At  position,  3-,  methyl,  ethyl,  normal  and  isopropyl,  iso-  and  second- 
ary butyl,  isoamyl,  allyl,  phenyl,  o-tolyl,  />-anisyl,  benzyl,  beta-naphthyl, 
CH2COOR,  CH2CONH2,  CH2CN,  C6H4COOR,  C6H4CONH2,  C6H4CN,  the 
amino  group  and  its  derivatives,  quinazolonyls,   and  dimethyl  dicarb- 
ethoxy  pyrrole. 

3.  At  position,  4-,  OH,  Cl,  and  OR. 

4.  On  the  benzene  nucleus-,  alkyls,  halogens,  nitro,  amino  (and  deriva- 
tives), and  COOH. 

In  the  various  series,  where  homologs  of  analogous  structure  are  com- 
pared, it  will  be  found  that  the  melting  point  falls  quite  steadily  with 
rise  in  molecular  weight,  the  iso  compounds  melting  higher  than  the 
isomers  carrying  normal  alkyls.  This  is  perhaps  not  so  surprising  since 
many  series  of  anthranilic  compounds  (for  example,  the  alkyl  and  acyl- 
amino  anthranilic  acids,  the  acylanthranilic  nitriles,  etc.)  exhibit  a  similar 
behavior. 

In  addition  to  the  4-quinazolones,  our  studies  have  included  also  the 
2-quinazolones  (2-hydroxyquinazolines),  2,4-dihydroxyquinazolines  (2,4- 

1  Bogert  and  May,  Loc.  cit. 

2  Compare  Fischer,  Ber.,  32,  1297  (1899). 

77 


792  ORGANIC   AND    BIOLOGICAL. 

dike  tote  trahydroquinazolines,    or   benzoylene    ureas),    and    a   few   other 
types. 

B.  Thioquinazolines. 

The  work  in  the  domain  of  the  oxygenated  quinazolines  led  quite  natur- 
ally to  the  production  of  bodies  of  analogous  structure  carrying  sulphur 
instead  of  oxygen,  and  known  as  the  4-thioquinazolone  or  quinazolthion  (4) 
type,1 

/N  =  Cr  N===CR 

C6H/  !       I£±  C6H4<  |    . 

\CS  .  NH  \C(SH)  :  N 

Since  anthranilamides,  as  noted,  easily  condense  to  quinazolines  by 
loss  of  water,  it  seemed  probable  that  the  corresponding  thioamides  would 
yield  thioquinazolines. 

/NH.COR  XN  =  CR 

C,H/  =C6H4<  |      +  H.O. 

\CS.NH,  NCS  .  NH 

and  the  results  corroborated  this  fully. 

The  acylanthranilic  thiamide  was  prepared  either  by  first  converting 
the  anthranilic  nitrile  to  the  amide  by  the  direct  addition  of  hydrogen 
sulphide  and  then  acylating,  or  by  first  acylatirig  and  then  adding  the  H2S: 

/NH, 

C6H/  +  O(COR), 

A       \CSNH, , 

t+H,S  I 

/NH,  |       /NH.COR  /N  =  CR 

r\     TT     £  s-\    TT     S  -    ,     £>.     TT     /  I  I        TT    £\ 

*\CN  A*    4^CS.NH2  4\CS .  NH 

+  O(COR), 
NH.COR 

H,S 

CN 


By  the  use  of  thiol  acids  (for  example,  thioacetic  acid)  in  sealed  tubes, 
the  thioquinazoline  was  obtained  direct.  The  thiol  acid  first  acylates 
the  amino  group.  The  by-product  of  this  acylation,  H2S,  cannot  escape 
from  the  tube  and  is  thus  forced  to  attach  itself  to  the  CN,  thereby  changing 
it  to  the  thioamide.  The  acylaminothioamide  then  passes  to  the  thio- 
quinazoline by  loss  of  water. 

As  comparatively  few  thiol  acids  are  readily  available,  we  made  our 
reaction  more  widely  applicable  by  substituting  the  acid  anhydride  with 
sodium  sulphide  for  the  thiol  acid.  Thus,  when  anthranilic  nitrile  is 
heated  with  acetic  anhydride  and  sodium  sulphide  in  open  flasks  or, 
better,  in  sealed  tubes,  the  anhydride  first  acetylates  the  amino  group 
with  formation  of  acetic  acid  as  the  by-product.  The  latter  then  attacks 
the  sodium  sulphide,  setting  free  hydrogen  sulphide  and  forming  sodium 
acetate.  The  hydrogen  sulphide  converts  the  acetoanthranilic  nitrile 
to  the  thioamide,  which  then  splits  out  water  and  gives  the  quinazoline, 
the  sodium  acetate  possibly  assisting  in  the  elimination  of  this  molecule 
of  water. 

These  thioquinazolines  crystallize  in  beautiful  yellow  needles  or  prisms 

when  alcohol  is  used  as  the  solvent.     By  virtue  of  the  — CS.NH —  7""^ 

— C(SH)  :  N —  group,   they  dissolve  freely  in  solutions  of  the  caustic 

1  Bogert,  Breneman  and  Hand,  THIS  JOURNAL,  25,  372  (1903);  Bogert  and  Hand, 

Ibid.,  25,  935  (1903)- 

78 


RECENT   INVESTIGATIONS   IN  THE   QUINAZOLINE   GROUP.  793 

alkalies  and  are  re  precipitated  therefrom  by  carbon  dioxide  or  by  acetic 
acid. 

Like  the  corresponding  oxygen  compounds,  the  melting  point  of  the 
2-alkyl  derivatives  steadily  falls  with  rise  in  molecular  weight,  the  iso 
compounds  melting  higher  than  the  isomers  of  normal  structure. 

In  the  course  of  the  investigation,  we  have  used  both  simple  and  sub- 
stituted anthranilic  acids. 

C.  Naphthotetrazines. 

Our  syntheses  of  the  simple  quinazolines  having  resulted  so  satis- 
factorily, we  decided  to  attempt  the  synthesis  of  compounds  of  the  follow- 
ing types, 

N  N  N 


N 
.     \/  \/ 

N 
( 1,3,6,8-Naphthotetrazine)         ( 1,3,7,9-Naphthotetrazine) 

and  in  this  were  equally  fortunate. 

Naphthotetrazines  of  both  types  were  prepared  from  the  bis-acyl- 
anthranils  of  the  appropriate  diaminophthalic  acid  and  various  primary 
amines,1 

RCO.Nv  JST.COR  RC:Nv  .N  =  CR 

OCf          *^CO  R'N.CCK          *\CO  .  NR' 

as  well  as  from  the  diaminophthalic  acids  themselves  by  reactions  similar 
to  those  employed  for  the  synthesis  of  the  simple  quinazolines.  The 
diaminophthalic  acids  used,  which  must  be,  of  course,  of  anthranilic 
structure,  were 


HO°C\/\/NH'  H,N  NH, 


-_Z-[//NS//N^COOH  HOOC'S^  \COOH 

(3,6-Diamino-i,4-phthalic  acid)  (4,6-Diamino-i,3-phthalic  acid) 
These  acids,  as  can  be  seen  by  a  glance  at  their ,  graphic  formulas,  are 
only  double  anthranilic  acids,  and  undergo  similar  reactions,  the  former 
yielding  the  1,3,6,8-naphthotetrazines,  and  the  latter  the  1,3,7,9-isomers. 
1,3,6,8-Naphthotetrazines  were  also  obtained  by  condensing  suc- 
cinylosuccinic  esters  with  amidines:2 

HN .HJ*OjCO.C.CH,CJOH~H  N  :  CR 

I "  + ii     ir  ~+     i  = 

RC : NH_HO  C.CHaC.CO:QR  HJNH 

HN.CO.C.CH..C.N:  CR 

RC:N.C.CH,.CCONH 

All  of  these  naphthotetrazine  derivatives  so  far  obtained  by  the  above 
processes  are  either  infusible  or  melt  very  high.  They  are  insoluble  in 
the  ordinary  neutral  organic  solvents.  When  they  carry  the  — NH.CO — 

1  Bogert  and  Nelson,  THIS  JOURNAL,  29,  729  (1907);  Bogert  and  Kropff,  Ibid., 
31,  1071  (1910). 

2  Bogert  and  Dox,  Ibid.,  27,  1127  and  1302  (1905). 

79 


794  ORGANIC  AND   BIOLOGICAL. 

x  >  — N  :  C(OH) —  group,  they  dissolve  readily  in  solutions  of  the 
caustic  alkalies,  whence  they  are  reprccipitated  by  carbon  dioxide  or 
by  acetic  acid. 

The  naphthotetrazine  prepared  from  guanidine  and  succinylosuccinic 
ester  gives  a  sodium  salt  crystallizing  in  beautiful  yellow  needles  or  prisms 
which  have  a  magnificent  greenish  fluorescence. 

This,  in  a  very  hasty  and  imperfect  way,  indicates  the  main  lines  along 
which  this  particular  field  of  investigation  has  been  developed.  It  would 
only  weary  you  to  refer  even  hurriedly  to  the  many  subordinate  lines 
of  investigation  radiating  from  these  main  ones,  necessitating  or  resulting 
in  the  synthesis  of  many  hundreds  of  new  organic  substances.  I  can  only 
say,  as  I  did  at  the  outset  of  this  address,  that  it  has  all  been  most  interest- 
ing to  us,  and  that  we  are  still  carrying  on  the  work. 


The  articles  published  in  the  progress  of  these  researches  are  listed 
below.  They  all  have  appeared  in  The  Journal  of  the  American  Chemical 
Society,  to  which  the  volume  numbers  refer : 

1900  i.  A  new  synthesis  in  the  quinazoline  group.     M.  T.  Bogert  and  A.  H.  Gotthelf, 
THIS  JOURNAL,  22,  129. 

2.  The   direct   synthesis   of   ketodihydroquinazolines   from   orthoamino  acids. 
M.  T.  Bogert  and  A.  H.  Gotthelf,  Ibid.,  22,  522. 

1901  3.  The  synthesis  of  alkyl  ketodihydroquinazolines  from  anthranilic  acid.     A. 
H.  Gotthelf,  Ibid.,  23,  611. 

1902  4.  The  synthesis  of    alkyl    ketodihydroquinazolines    from  anthranilic  nitrile. 
M.  T.  Bogert  and  W.  F.  Hand,  Ibid.,  24,  1031. 

I9°3     5-  The  synthesis  of  alkyl  thio ketodihydroquinazolines  from  anthranilic  nitrile. 
M.  T.  Bogert,  H.  C.  Breneman  and  W.  F.  Hand,  Ibid.,   25,  372. 

6.  3,5-Bibrom-2-aminobenzoic  acid;  its  nitrile  and  the  synthesis  of  quinazolines 
from  the  latter.     M.  T.  Bogert  and  W.  F.  Hand,  Ibid.,  25,  935. 

1905  7.  The  synthesis    of    5-nitro-4- ketodihydroquinazolines  from  6-nitro-2-amino- 
benzoic  acid,  6-nitro-2-acetylaminobenzoic  acid,  and  from  the  corresponding  nitro 
acetylanthranil.     M.  T.  Bogert  and  V.  J.  Chambers,  Ibid.,  27,  649. 

8.  The  condensation  of  succinylosuccinic   acid    diethyl  ester  with  guanidine. 
A  derivative  of  1,3,5,7-naphthotetrazine,  a  new  heterocycle.      M.  T.  Bogert  and  A. 
W.  Dox,  Ibid.,  27,  1127. 

9.  Some  acyl  derivatives  of  homoanthranilic  nitrile,  and  the  7-methyl-4-ketodi- 
hydroquinazolines  prepared  therefrom.      M.  T.  Bogert  and  A.  Hoffman,  Ibid.,  27, 
1293. 

10.  The  condensation  of  succinylosuccinic  acid  diethyl  ester  with  acetamidine: 
2,6-dimethyl-4,8-dihydroxy-9,io-dihydro-i,3,5,7-napthotetrazine.    M.  T.  Bogert  and 
A.  W.  Dox,  Ibid.,  27,  1302. 

11.  The  synthesis    of    2-methyl-5-nitro-4-ketodihydroquinazolines    from  6-nitro 
acetanthranil  and  primary  amines.     M.  T.  Bogert  and  H.  A.  Seil,  Ibid.,  27,  1305. 

12.  The    synthesis    of    7-nitro-2-alkyl-4-ketodihydroquinazolines    from  4-nitro 
acetanthranilic  acid  and  from  4-nitro  acetanthranil.     M.  T.  Bogert  and  S.  H.  Steiner, 
Ibid.,  27,  1327. 

13.  5-Brom-2-aminobenzoic  acid  and  some  of  its  derivatives.     M.  T.  Bogert  and 
W.  F.  Hand,  Ibid.,  27,  1476. 

1906  14.  The     preparation     of     6-brom-4-ketodihydroquinazolines     from     5-brom-2 
aminobenzoic  acid  and  certain  of  its  derivatives.     M.  T.   Bogert  and  W.  F.  Hand, 
Ibid,,  28,  94, 

80 


RECENT   INVESTIGATIONS   IN  THE  QUINAZOUNE   GROUP.  795 

15.  On    5-amino-4-ketodihydroquinazolines    and    5-amino-2-methyl-4-ketodihy- 
droquinazolines.     M.  T.  Bogert  and  V.  J.  Chambers,  Ibid.,  28,  207. 

16.  On    the   condensation   of   succinylosuccinic   esters   with   amidines.     M.    T. 
Bogert  and  A.  W.  Box,  Ibid.,  28,  398. 

17.  On   a   3-aminoquinazoline   and    the   corresponding   3,3'-diquinazolyl,    from 
6-nitro  acetanthranil  and  hydrazine  hydrate.     M.  T.  Bogert  and  H.  A.  Sell,  Ibid.,  28, 
884. 

18.  Synthesis  of  6-nitro-2-methyl-4-ketodihydroquinazolines  from  5-nitro  acetan- 
thranil and  primary  amines.     M.  T.  Bogert  and  E.  P.  Cook,  Ibid.,  28,  1449. 

1907  19.  The  synthesis  of  quinazoline  carboxylic  acids  from  4-aminoisophthalic  acid 
and  from  aminoterephthalic  acid.     M.  T.  Bogert,  J.  D.  Wiggin  and  J.  E.  Sinclair, 
Ibid.,  29,  82. 

20.  A  strange  case  of  poisoning.     M.  T.  Bogert,  Ibid.,  29,  239. 

21.  On    2,3-dialkyl-4-quinazolones   and    the    products   obtained    by   alkylating 
2-alkyl-4-quinazolones  (2-alkyl-4-hydroxyquinazolines).     M.  T.  Bogert  and  H.  A. 
Sell,  Ibid.,  29,  517. 

22.  The    synthesis   of    1,3,6,8-naphthotetrazines   from    paradiaminoterephthalic 
acid  and  from  certain  of  its  derivatives.     M.  T.  Bogert  and  J.  M.  Nelson,  Ibid.,  29, 
729. 

1908  23.  On  certain  7-nitro-2-methyl-4-quinazolones  from  4-nitroacetanthranil.     M. 
T.  Bogert  and  W.  Klaber,  Ibid.,  30,  807. 

1909  24.  3-Amino-o-phthalic  acid  and  certain  of  its  derivatives.     M.  T.  Bogert  and 
F.  L.  Jouard,  Ibid.,  31,  483. 

25.  On  certain  quinazoline  oxygen  ethers  of  the  type  — N:C(OR) —  and  the 
isomeric  — NR.CO —  compounds.     M.  T.  Bogert  and  C.  E.  May,  Ibid.,  31,  507. 

26.  On  some  amino  and  nitroamino  derivatives  of    benzoic,   metatoluic    and 
metaphthalic  acids.     M.  T.  Bogert  and  A.  H.  Kropff,  Ibid.,  31,  841. 

27.  On  2-methyl-3-amino-4-quinazolone  and  certain  of  its  derivatives.     M.  T. 
Bogert  and  R.  A.  Gortner,  Ibid.,  31,  943. 

28.  On    6-methyl-7-aminoquinazolones,     7-nitroquinazolone-6-carboxylic    acids, 
and  1,3,7,9-naphthotetrazines.     M.  T.  Bogert  and  A.  H.  Kropff,  Ibid.,  31,  1071. 

1910  29.  On  oxalyl  anthranilic  compounds  and  quinazolines  derived  therefrom.     M.  T. 
Bogert  and  R.  A.  Gortner,  Ibid.,  32,  119. 

HAVEMEYBR  LABORATORIES,  COLUMBIA  UNIVERSITY, 
March  2*,   1910. 


A  REVIEW  OF  DISCOVERIES  ON  THE   MUTAROTATION  OF  THE 

SUGARS.1 

By  C.  S.  HUDSON. 
Received  May  9,  1910. 

Dubrunfaut2  discovered  in  1846  that  the  specific  rotation  of  a  freshly 
prepared  cold  solution  of  crystalline  glucose  decreases  from  an  initial 
value  of  about  110°  to  become  constant  at  52°.  This  phenomenon  he 
named  birotation  but  later  discoveries  have  shown  the  name  to  be  in- 
appropriate and  the  better  term  mutarotation,  which  was  introduced  by 
Lowry3  in  1899,  has  generally  replaced  it,  though  the  word  muliirotation 

1  Presented  at  the  Second  Decennial  Celebration  of  Clark  University,  Worcester, 
Mass.,  Sept.  15,  1909. 

2  Ann.  chim.  phys.,  18,  99-107  (1846);  21,  178-80  (1847);  Compt.  rend.,  23,  38-44 
(1846). 

8  /.  Chem.  Soc.,  75,  212-5  (1899). 

8l 


890  ORGANIC  AND   BIOLOGIC AL,. 

is  also  in  use.  In  addition  to  glucose  the  following  crystalline  sugars 
have  been  found  to  show  mutarotation:  lactose,1  galactose,2  arabinose,3 
maltose,4  xylose,5  fructose,6  fucose,7  rhamnose,8  mannose,9  rhodeose,10 
gentiobiose,11  melibiose,12  perseulose,13  and  several  rare  synthetic  sugars. 
All  of  these  sugars  reduce  Fehling's  solution  and  combine  with  phenyl- 
hydrazine,  proving  that  they  are  aldoses  or  ketoses  and  contain  the 
carbonyl  group;  on  the  other  hand  such  sugars  as  sucrose,  raffinose, 
gentianose,  and  stachyose,  and  the  polysaccharides  starch,  inulin,  mannan, 
etc.,  and  the  glucosides  salicin,  amygdalin,  helicin,  arbutin,  etc.,  none 
of  which  show  the  characteristic  reactions  for  the  carbonyl  group,  do  not 
exhibit  mutarotation.  This  proves  that  the  mutarotation  is  in  some 
way  dependent  upon  the  carbonyl  group. 

After  Dubrunfaut's  great  discovery  the  next  important  observation  on 
mutarotation  was  made  by  E.  O.  Erdmann14  in  1855,  who  noticed  that 
lactose  occurs  in  two  crystalline  modifications,  one  having  a  higher  rota- 
tion (86°)  than  that  of  the  stable  solutions  (52°),  and  the  other  a  lower 
rotation  (36°),  and  each  form  showing  mutarotation  towards  the  same 
final  rotation  (52°).  Erdmann  measured  the  rates  at  which  each  form 
changes  in  rotation  to  that  of  the  stable  solution,  but  did  not  notice 
that  the  rates  are  the  same  in  value  and  that  this  fact  is  of  much  theoretical 
significance.  Many  years  later,  after  the  principles  of  chemical  dynamics 
became  better  known,  the  author15  showed  that  these  equal  rates  prove 
that  the  two  changes  of  rotation  are  not  different  reactions  but  are  opposite 
parts  of  one  balanced  reaction.  In  this  way  the  mutarotation  of  lactose, 
and  what  is  true  of  this  sugar  is  doubtless  true  of  all  which  show  mutarota- 
tion, was  proved  to  belong  to  the  great  class  of  balanced  reactions.16 

In  1859  Anthon17  noticed  that  crystalline  glucose  forms  its  saturated 
solutions  in  cold  water  very  slowly  even  when  the  mixing  is  vigorous; 
this  fact  was  discovered  for  lactose  by  Mills  and  Hogarth18  in  1879.  It 
is  now  known  that  this  slowness  of  the  process  of  solution  is  caused  by  the 
same  slow  balanced  chemical  reaction,  involving  the  carbonyl  group, 

1  E.  O.  Erdmann,  Fortschritte  Physik.,  p.  13;   Fortschritte  Chemie,  p.  671  (1855). 

2  Pasteur,  Compt.  rend.,  42,  347-51  (1856). 

3  Parcus  and  Tollens,  Ann.,  257,  160-78  (1890). 

4  Soxhlet,  /.  prakt.  Chem.,  21,  283  (1880). 

8  Koch,  Pharm.  Ztg.   Riissland,   25,   619,  635,  651,  667,  683,  699,  730,  747,  763 
(1886). 

6  Jungfleisch  and  Grimbert,  Compt.  rend.,  107,  390-3  (1888). 

7  Guenther  and  Tollens,  Ber.,  23,  2585-6  (1890). 

8  Parcus  and  Tollens,  Loc.  cit. 

9  Van  Ekenstein,  Rec.  tra-v.  chim.,  15,  221-4  (1896). 

10  Z.  Zuckerind.  Bohmen,  25,  297  (1902). 

11  Bourquelot  and  H6rissey,  Ann.  chim.  phys.    27,  397-432  (1902). 
11  Z.  Ver.  d.  Zuckerind.,  53,  1050-9  (1903). 

13  Bertrand,  Compt.  rend.,  147,  201-3  (1908). 

14  Loc.  cit.     Also  Ber.,  13,  2180-4  (1880). 
18  Z.  physik.  Chem.,  44,  487-94  (1903). 

18  Using  the  same  method  Meyer  later  proved  this  for  glucose,  Z.  physik.  Chem., 
62,  74  (1908).     Cf.  also  Roux,  Ann.  chim.  phys.,  30,  422-32  (1903). 

17  Dingier**  poly.  /.,  151,  213-23  (1859);  155,  386-8  (1860);  166,  69-71  (1862). 
11  Proc.  Roy.  Soc.  London,  28,  273-9  (1879). 

82 


DISCOVERIES  ON  THE   MUTAROTATION   OF  THE   SUGARS.  89! 

which  causes  the  mutarotation,  and  that  it  is  a  general  property  of  all  the 
aldehyde  and  ketone  sugars.1 

The  first  attempt  to  find  the  physical  law  which  governs  the  rate  of  the 
mutarotation  was  made  by  Mills  and  Hogarth2  in  1879,  but  the  result  was 
only  an  empirical  formula  and  must  be  regarded  as  unsatisfactory.  It 
is  to  Urech3  that  we  owe  the  first  real  progress  in  this  line.  He  showed 
by  a  series  of  experiments  during  1882-5  that  the  mutarotation  follows 
the  law  of  unimolecular  reactions.  It  is  interesting,  and  to  some  minds 
instructive,  to  note  that  this  correct  beginning  in  the  physico-chemical 
study  of  the  long  unsolved  mutarotation  reaction  was  coincident  in  time 
with  the  beginning  of  the  modern  theory  of  solutions  and  chemical  dynam- 
ics. There  can  be  little  doubt  that  Urech's  experiments,  which  are 
the  starting  point  of  all  exact  work  on  mutarotation,  were  suggested  by 
the  advances  that  were  being  made  at  that  time  in  the  study  of  chemical 
dynamics  by  the  new  physico-chemical  school. 

In  1888  Brown  and  Morris4  and  Arrhenius5  observed  that  the  freezing 
temperatures  of  glucose  solutions  remain  unchanged  during  the  process  of 
mutarotation,  which  proves  that  the  reaction  which  causes  mutarotation 
is  not  a  polymerization  or  dissociation  of  the  sugar.  More  recently 
Roth8  has  detected  a  slight  change  in  freezing  temperature  of  concentrated 
solutions  of  anhydrous  glucose  on  standing  but  this  is  doubtless  due  to 
hydration  and  does  not  alter  the  conclusion  from  the  work  of  Brown  and 
Morris  and  Arrhenius,  because  a  polymerization  or  dissociation  would  also 
affect  the  freezing  point  of  dilute  solutions,  and  the  investigators  are  all 
agreed  that  such  an  effect  is  not  discernible. 

In  1890  O'Sullivan  and  Tompson7  noticed  that  the  invert  sugar  which 
is  produced  by  the  hydrolytic  action  of  the  enzyme  invertase  on  sucrose 
shows  mutarotation;  this  fact  was  later  investigated  by  E.  F.  Armstrong8 
and  has  been  precisely  studied  lately  by  the  author.9  These  researches 
have  shown  that  the  glucose  which  is  liberated  from  sucrose  is  a-glucose 
and  the  fructose  is  a  hitherto  unknown  form  of  this  hexose,  a-fructose; 
these  facts  show  that  sucrose  has  the  constitution  a-glucose  <  >  a-fructose. 
The  new  form  of  fructose  has  not  as  yet  been  obtained  crystalline.  This 
method  for  determining  the  constitution  of  the  polysaccharides  by  study- 
ing the  mutarotation  of  the  sugars  which  are  formed  by  their  enzymotic 
hydrolysis  was  first  used  by  E.  F.  Armstrong2  in  his  correlation  of  the 
a-  and  /?-methylglucosides  with  the  a-  and  /?-glucoses.  In  applying  the 
method  to  other  substances  such  as  cane  sugar  where  two  mutarotating 
sugars  are  formed  at  the  same  time  it  is  necessary  to  extend  the  theoretical 
considerations;  a  mathematical  theory  of  the  modified  method  of  Arm- 

1  Hudson,  Z.  physik.  Chem.,  44,  487-94  (1903);  THIS  JOURNAL,  26,  1065-82  (1904). 
1  Loc.  cit. 

*  Ber.,  15,  2130-3   (1882);  16,  2270-1   (1883);  17,   I547~5O  (1884);  18,  3047-60 
(1885). 

*  J.  Chem.  Soc.,  53,  610-21  (1888). 

6  Z.  physik.  Chem.,  2,  491-505  (1888). 

*  Ibid.,  43,  539-64  (1903). 

7  /.  Chem.  Soc.,  57,  920  (1890). 

8  Ibid.,  83,  1305-13  (1903)- 

*  THIS  JOURNAL,  30,  1160-6,  1564-83  (1908);  31,  655-64  (1909). 

83 


892  ORGANIC  AND   BIOLOGICAL. 

strong  and  an  experimental  demonstration  of  it  has  recently  been  pub- 
lished by  the  author.1 

In  1895  Charles  Tanret2  discovered  a  new  form  of  crystalline  glucose 
which  was  found  to  have  a  specific  rotation  lower  than  that  of  the  stable 
solution  (52°),  though  its  value  increased  to  this  on  standing.  This 
discovery  is  the  complement  to  Dubrunfaut's  and  the  two  must  cause 
chemists  the  world  over  to  be  grateful  to  French  science,  because  more 
fruitful  single  discoveries  in  the  chemistry  of  the  carbohydrates  have 
hardly  been  made.  Tanret  found  the  final  rotation  of  glucose  solutions 
to  be  the  same  whether  the  solution  is  made  from  the  higher  or  the  lower 
initially  rotating  form.  He  interpreted  his  results  as  proving  that  three 
forms  of  glucose  exist,  one  of  high  rotation,  one  of  low,  and  the  third  the 
form  to  which  each  of  these  changes  in  aqueous  solution.  About  the  same 
time  Tanret  isolated  similar  new  crystalline  forms  of  rhamnose,  galactose 
and  arabinose,  and  obtained  Erdmann's  lower  rotating  form  of  lactose 
practically  pure.  Tanret's  striking  discoveries  immediately  caused  new 
interest  to  be  taken  in  the  problem  of  mutarotation.  In  1899  Lowry1 
advanced  the  view  that  the  mutarotation  of  glucose  is  caused  by  a  balanced 
reaction  between  the  highest  and  lowest  rotating  forms  of  the  sugar,  a 
view  which  may  be  expressed  by  the  equation  a-glucose  ~^~*'  {3-glucose. 
This  explanation  is  essentially  different  from  any  that  preceded  it  and 
later  investigations  have  proved  it  to  be  entirely  correct.  On  the  other 
hand,  Lowry  did  not  support  this  hypothesis  with  any  direct  proof  and  it 
remained  without  such  proof  for  several  years.  In  1902*  the  author 
published  the  same  view  as  an  explanation  of  the  mutarotation  of  lactose, 
being  at  that  time  unacquainted  with  the  publication  of  Lowry.  The 
explanation  may  be  expressed  by  the  equation  a-lactose  ~j~>'  /?-lactose, 
and  experimental  evidence  for  the  view  was  given  by  measurements  on 
the  heats  of  solution  of  the  three  forms  of  lactose,  which  showed  that  the 
stable  form  to  which  a-  and  ^-lactose  change  in  solution  is  not  a  chemical 
individual,  as  Tanret  had  supposed,  but  is  a  mechanical  mixture  of  a- 
and  /Mactoses.  In  1903  the  author4  measured  the  slow  maximum  rate  of 
solution  of  a-lactose  and  showed  that  the  slowness  of  dissolving,  which 
had  been  discovered  by  Mills  and  Hogarth,1  is  caused  by  the  balanced 
reaction  which  produces  the  mutarotation.  By  quantitative  measure- 
ments the  hypothesis  of  the  balanced  reaction  was  tested  and  proved, 
and  the  explanation  which  these  measurements  gave  of  the  mutarotation 
of  lactose  was  immediately  accepted  by  such  an  authority  as  Nernst.5 
In  the  same  year  Lowry6  published  similar  experiments  on  glucose  and 
proved  the  suggestion  which  he  had  advanced  in  1899.  These  questions 
of  priority  are  here  stated  for  the  reason  that  E.  F.  Armstrong7  has  recently 
claimed  for  Lowry  the  discovery  of  the  balanced  reaction  which  causes 
the  mutarotation,  a  claim  which  in  the  opinion  of  the  author  is  entirely 
too  broad. 

1  Loc.  cit. 

2  Bull.  soc.  chim.,  15,  195-205,  349-61;  17,  802-5. 
*  Princeton  Univ.  Bull.,  April,  1902. 

4  Z.  physik.  Chem.,  44,  487-94  (1903). 
8  "  Theoretische  Chemie,"  ed.  1904. 

6  Proc.  Chem.  Soc.,  19,  156-7  (1903);  20,  108-9  (1904). 

7  "The  Simple  Carbohydrates  and  Glucosides,"  p.  8. 

84 


DISCOVERIES  ON  THE   MUTAROTATION   OF  THE   SUGARS.  893 

A  very  fruitful  idea  was  advanced  by  Llppmann1  in  1895  in  the  sugges- 
tion that  the  lactonic  formula  for  glucose  predicts  two  possible  forms  of 
the  sugar  on  account  of  the  asymmetry  of  the  end  carbon  atom,  the  two 
structures  being 

, O -,  /H 

CH2OH.CHOH.CH.CHOH.CHOH.C<         and 

XOH 

r-      — O n   /OH 

CH2OH.CHOH.CH.CHOH.CHOH.C<^       , 

This  suggestion,  after  a  slight  development  by  Simon,2  was  made  more 
probable  by  Armstrong's  discovery,3  that  the  a-  and  /9-forms  of  methyl 
glucoside  are  hydrolyzed  by  enzymes  to  give  methyl  alcohol  and  the 
a-  and  /?-forms  of  glucose  respectively.  As  the  methyl  glucosides  show  no 
aldehyde  reactions  the  lactonic  formulas  have  always  been  chosen  for 
them,  the  hydroxyl  of  the  end  carbon  atom  in  the  structures  shown  above 
being  replaced  by  the  group  OCH3.  Armstrong's  discovery  indicates 
that  similar  structures  probably  apply  to  the  forms  of  glucose.  This 
suggestion  received  final  proof  in  1909  when  the  author*  showed  that  certain 
numerical  relations  which  can  only  be  explained  by  the  assumption  of 
such  lactonic  structures  for  the  two  forms  of  the  sugar,  hold  all  through 
the  sugar  group.  If  the  rotation  of  the  end  carbon  atom  is  B  for  one 
structure  it  must  be  — B  for  the  other,  and  if  A  is  the  rotation  of  the 
remaining  asymmetric  carbon  atoms,  which  are  common  to  both  struc- 
tures, the  total  rotation  of  the  one  structure  is  A  +  B,  and  of  the  other 
structure  A  —  B,  the  difference  between  the  two  total  rotations  being 
then  2B.  This  rotation  B  applies  to  all  the  aldoses  because  they  contain 
the  same  end  asymmetric  carbon,  therefore  the  difference  between  the 
molecular  rotations  of  the  a-  and  /3-forms  of  all  the  aldose  sugars  should 
be  a  constant  quantity  if  the  sugars  have  the  two  isomeric  lactonic  struc- 
tures. The  molecular  rotatory  powers  of  the  two  forms  of  lactose,  glucose, 
arabinose  and  galactose  were  found  indeed  to  differ  by  the  quantities 
17600,  16000,  16200,  and  15700,  which  are  sufficiently  alike  to  show  that 
the  theory  is  correct  and  that  the  two  forms  of  each  of  the  mutarotating 
sugars  have  the  stereomeric  lactonic  structures.  Certain  other  similar 
conclusions  from  the  same  theory  were  also  found  to  agree  with  the 
rotatory  powers  of  the  sugars  and  their  glucosidic  derivatives. 

The  catalytic  action  of  various  substances  on  the  mutarotation  reaction 
has  been  investigated  by  various  chemists.5  These  researches  have 
shown  that  only  acids  and  alkalies  have  a  strong  action.  Osaka6  made 
the  first  quantitative  study  of  the  relation  between  acidity  or  alkalinity 
and  catalytic  action  and  found  that  the  catalysis  is  proportional  to  the 
concentration  of  the  hydroxyl  ions  and  proportional  to  the  square  root 

1  "  Die  Chemie  der  Zuckerarten,"  ed.  1895,  pp.  130,  990,  992. 

2  Compt.  rend.,  132,  487-90  (1901). 

3  Loc.  cit. 

4  THIS  JOURNAL,  31,  66-86  (1909). 

6  Levy,  Z.  physik.  Chem.,  17,  301-24  (1895);  Trey,  Ibid.,  18,  193-218  (1895);  22, 
424-63  (1897);  46,  620-719  (1903);  Simon  and  Benard,  Compt.  rend.,  132,  564-6  (1901); 
Lowry,  /.  Chem.  Soc.,  83,  1314-23  (1903). 

6  Z.  physik.  Chem.,  35,  661-706  (1898). 

85 


894  ORGANIC  AND   BIOLOGICAL. 

of  that  of  the  hydrogen  ions.  Later  the  author1  showed  that  the  pro- 
portionalities are  somewhat  different  from  this  and  that  the  rate  of  the 
mutarotation  of  glucose  is  related  to  the  acidity  and  alkalinity  of  the 
solution  by  the  expression  rate  =  A  +  B(H')  +  C(OH'),  where  A,  B, 
and  C  are  constants  at  constant  temperature.  This  formula  has  lately 
been  used  as  the  basis  of  a  new  method  for  measuring  the  electrolytic 
dissociation  of  water.2  A  satisfactory  explanation  of  the  fact  that  acids 
and  alkalies  are  enormously  powerful  catalysts  of  the  mutarotation  while 
all  other  substances  are  without  comparable  action  is  lacking. 

The  sugars  glucose,  lactose,  galactose,  rhamnose,  melibiose,  arabinose, 
maltose,  xylose  and  some  others  occur  as  monohydrates  and  these  have 
generally  been  regarded  as  hydrated  aldehydes  without  lactonic  structure 
and  thus  intermediate  forms  between  the  two  lactonic  a-  and/3-forms 
of  the  sugars.  The  freshly  prepared  solutions  of  these  monohydrates 
are  identical  in  properties  with  such  solutions  of  one  of  the  anhydrous 
lactonic  forms  of  the  sugars  and  it  is  therefore  to  be  concluded  that  the 
equilibrium  between  this  lactonic  form,  whichever  it  may  be,  and  the 
monohydrate  is  established  instantly.  For  most  of  the  sugars  the  lactonic 
form  which  is  thus  in  instantaneous  equilibrium  with  the  monohydrate 
is  the  a-form,  but  for  one  sugar  at  least,  maltose,  it  is  the  /3-form.  The 
mutarotation  reaction  may  then  be  considered  to  be  the  slow  change  of 
the  monohydrate  into  the  other  lactonic  form  by  a  reversible  reaction, 
or  in  the  form  of  an  equation, 

a-sugar  +  H2O  "7"*'  monohydrate  ~^~^~  /?-sugar  +  H3O. 

(i)  .(2) 

For  most  of  the  sugars  the  reaction  i  is  instantaneous  in  comparison 
with  2,  which  is  therefore  the  mutarotation  reaction,  but  for  maltose  the 
relations  are  reversed.  Why  the  monohydrate  should  change  instantly 
to  the  a-form  for  some  sugars,  but  to  the  /9-form  for  others  is  entirely 
unknown  and  is  a  most  interesting  problem. 

The  mutarotation  reaction  is  general  to  all  the  aldehyde  and  ketone 
sugars.  It  may  indeed  be  called  the  fundamental  reaction  of  the  sugar 
group.  While  its  cause  remained  unknown  during  the  half  century 
following  its  discovery,  the  last  decade  has  brought  a  full  explanation 
of  it.  The  principal  facts  regarding  it  have  been  accurately  measured 
and  correlated.  On  the  other  hand  the  application  of  these  facts  to  the 
elucidation  of  the  chemical  and  biological  reactions  of  the  sugars,  in 
every  one  of  which  mutarotation  plays  a  part,  has  just  begun,  but  it  is 
even  now  apparent  that  the  unfolding  chemistry  of  the  polysaccharides 
is  to  be  largely  a  development  of  the  mutarotation  reaction. 

BUREAU  OF  CHEMISTRY,  U.  S.  DEPARTMENT  OF  AGRICULTURE, 
WASHINGTON,  D.  C. 

1  THIS  JOURNAL,  29,  1571-6  (1907). 
1  Ibid.,  31,  1136-8  (1909). 


86 


OUTLINE  OF  A  THEORY  OF  ORGANIC  CHEMISTRY  FOUNDED  ON 
THE  LAW  OF  ENTROPY.1 

BY  ARTHUR  MICHAEL. 
Received  June  27,  1910. 

There  appears  to  be  no  generalization  in  science  more  firmly  estab- 
lished than  the  second  law  of  thermodynamics,  which  demands  that 
every  spontaneous  chemical  change  shall  be  accompanied  by  an  increase 
of  entropy,  and  that  the  system  shall  endeavor  to  realize  this  increase 
to  its  maximum  extent. 

Since  the  law  of  entropy  represents  the  fundamental  principle,  under- 
lying and  regulating  all  chemical  phenomena  occurring  in  nature,  it  must 
necessarily  be  the  correct  scientific  basis  for  the  theory  of  organic  chemis- 
try. But  it  is  a  curious  fact  that  there  has  been  as  yet  little  attempt 
to  use  this  basic  chemical  principle  in  connection  with  organic  theory; 
this  theory  has  been  developed  along  lines  so  mechanical  in  their  charac- 
ter that  it  is  perhaps  no  exaggeration  to  speak  of  them  as  essentially 
pictorial.  This  unilateral,  mechanical  development  is  due  largely  to 
the  interpretation  of  the  phenomenon  called  valency;  and,  if  we  are  to 
incorporate  the  law  of  entropy  into  chemical  theory,  it  is  here  that  our 
theoretical  conceptions  will  require  a  radical  modification. 

Before  entering  a  discussion  of  the  subject  of  valency,  we  shall  men- 
tion a  conception  of  the  chemical  genesis  of  matter,  since  it  prepares  the 
way  for  the  theoretical  views  which  follow.  A  simple  hypothesis  is  to 
assume  that  cosmos  was  originally  made  up  of  two  kinds  of  matter, 
which  were  the  carriers  of  two  kinds  of  chemical  energy,2  and  that  the 
temperature  of  the  system  was  inconceivably  low.  Chemical  energy, 
as  it  now  appears  to  us,  exists  in  two  conditions.  One  of  these  is  freely 
and  perfectly  convertible  into  less  active  chemical  energy  and  into  various 
forms  of  physical  energy ;  and  this  less  active  chemical  energy  can  be  recon- 
verted into  the  active  form  only  partially  and  then  with  comparative 
difficulty.  We  shall  designate  the  active  form  free,  the  relatively  inac- 
tive form,  bound  chemical  energy,3  and,  as  the  transformations  of 
chemical  energy  must  have  obeyed  the  law  of  entropy  since  the 
beginning  of  cosmos,  the  original  corpuscles  were  exclusively  carriers 
of  free  chemical  energy,  and  the  accumulation  of  bound  chemical  energy 
and  the  various  forms  of  physical  energy  now  existing  have  been  grad- 
ually evolved  from  it. 

1  Address  delivered  at  the  Second  Decennial  Celebration  of  Clark  University, 
Worcester,  Mass.,  September  15,1909. 

1  To  distinguish  between  them  they  will  be  called  positive  and  negative,  but  this 
does  not  imply  any  connection  with  positive  and  negative  electricity. 

8  The  terms  free  and  bound  chemical  energy,  as  here  used,  are  not  to  be  confused 
with  the  terms  free  and  bound  energy  as  used  in  physical  chemistry,  with  which  they 
are  not  identical. 

87 


991  THEORY  OF  ORGANIC  CHEMISTRY. 

The  permanence  of  the  law  of  entropy  justifies  the  conclusion  that  the 
chemical  relations  which  existed  between  the  corpuscles  at  the  beginning 
were  similar  to  those  which  now  exist  between  the  atoms  and  the  mole- 
cules. We  may,  therefore,  assume  that  the  free  chemical  energy  of  unlike 
and  like  corpuscles  united  to  form  aggregations  in  which  the  corpuscles 
were  held  together  by  bound  chemical  energy.  At  first  the  chemical 
evolution  of  matter  must  have  been  accompanied  by  an  enormous  rise 
of  temperature,  but  later,  owing  to  the  decreasing  amount  of  free  chemical 
energy  in  the  cosmical  system,  a  period  must  have  come  when  the  loss 
of  heat  through  radiation  was  greater  than  its  formation,  and  then  the 
temperature  of  the  system  must  have  begun  to  decrease.  We  may 
assume,  too,  that  the  atoms  of  those  elements,  the  molecules  of  which 
now  show  the  greatest  stability  toward  heat,  were  formed  first  and  dur- 
ing the  hottest  period  of  cosmical  evolution.  Hence,  the  atoms  of  hy- 
drogen, and  those  of  the  non-metals,  with  small  atomic  weight,  repre- 
sent the  earliest  forms  of  atomic  matter. 

If  we  suppose  that  in  the  formation  of  the  atoms  of  certain  elements 
the  free  chemical  energy  of  the  corpuscles  was  very  largely  converted 
into  bound  chemical  energy  and  heat,  their  atoms  would  be  extremely 
inert  toward  other  atoms  and  incapable  of  uniting  with  each  other.  Such 
elementary  matter  is  represented  by  the  so-called  noble  gases,  in  the 
atoms  of  which  the  relation  of  free  corpuscular  to  free  atomic  chemical 
energy  is  analogous  to  that  of  free  atomic  to  free  molecular  chemical 
energy  in  the  atom  and  molecule  of  nitrogen.  Further,  if  we  suppose 
that  thermic,  or  other  conditions,  toward  the  end  of  the  corpuscular 
period  of  chemical  evolution  no  longer  permitted  a  sufficient  conversion 
of  free  into  bound  chemical  energy,  we  get  a  glimpse  into  the  genesis  of 
radioactive  matter,  the  atoms  of  which  contain  so  much  free  corpuscular 
chemical  energy  that  they  represent  a  reversible  system  and  are,  there- 
fore, gradually  breaking  down  into  smaller  parts,  which  then  rearrange 
according  to  the  changed  conditions  of  cosmos. 

Kekule",1  in  his  memorable  paper,  "Ueber  die  Constitution  und  die 
Metamorphosen  der  chemischen  Verbindungen, ' '  assumed  that  the  first 
phase  in  chemical  union  consists  in  molecules  attracting  each  other 
through  their  chemical  affinity,  and  that  a  sort  of  loosely  joined,  larger 
molecule  is  thus  formed.  It  is  obvious  that  the  formation  of  this 
"Kekule  poly  molecule"2  is  due  to  the  attraction  between  the  free  chem- 
ical energy  in  the  constituent  molecules,  and  that  it  proceeds  with  the 
conversion  of  more  or  less  free  into  bound  chemical  energy  and  heat — 
the  extent  of  this  change  determining  its  stability. 

Let  us  represent  the  free  chemical  energy  in  an  atom   by    a    point 

1  Ann.,  106,  141. 

2  Michael,  Ber.,  34,  4028;  39,  2140,  2570.     Am.  Chem.  J.,  39,  3;  41,  120. 

88 


ORGANIC   AND    BIOLOGICAL.  992 

and  the  bound  by  a  line,  and  let  the  number  of  the  points  and  the  length 
of  the  lines  be  a  rough  indication  of  the  changes  in  the  energy  values 
occurring  during  the  reaction.  If  we  assume  that  the  energies  of  un- 
like character  in  a  molecule  of  sodium  and  of  chlorine  are  approximately 
equal  in  value,  we  may  represent  the  energy  relations  in  sodium  and 
chlorine  by  • 

Na Na  Cl Cl 

and  the  "  polymolecule, "  representing  the  first  phase  in  their  interaction, 

by 

Na Na 

Cl Cl 

which  indicates  that  some  of  the  free  has  been  converted  into  bound 
chemical  energy.  The  free  chemical  energies  of  unlike  character  would 
then  strive  to  neutralize  each  other  as  completely  as  possible,  a  phase  of 
the  reaction  that  may  be  represented  by 

Na Na 

I 

Cl Cl 

and  then,  certainly  facilitated  by  the  enormous  "  internal  maximum  heat 

of  reaction,"1  the  bound  chemical  energies  between  Na  and  Na  and  Cl 
and  Cl  would  be  converted  into  bound  chemical  energy  between  Na  and 
Cl  and  Na  and  Cl ;  finally,  to  realize  a  phase  which  may  be  represented  by 

Na— Na 

I        I    . 

Cl— Cl 

At  this  point,  the  bound  chemical  energy  between  the  atoms  of  like  nature 
may  be  inadequate  to  hold  them  together,  and  the  complex  would  then 
break  down  into  two  molecules  of  NaCl.2 

What  happens  if  we  substitute  magnesium  in  the  place  of  sodium; 
that  is,  an  element  the  atom  of  which  contains  much  less  positive  energy? 
The  formation  of  a  "polymolecule,"  then  the  conversion  of  the  free 
chemical  energy  in  the  metallic  and  non-metallic  atoms  into  bound  be- 
tween metal  and  halogen;  but,  although  the  energy  in  the  sodium  mole- 
cule suffices  to  neutralize  that  in  the  chlorine  to  an  extent  that  the  com- 
plex breaks  down  into  two  molecules,  that  in  the  much  less  positive  mag- 

1  Wohl,  Ber.,  40,  2290.     That  part  of  the  free  and  bound  chemical  energy  is  con- 
verted into  heat  has  not  been  indicated. 

2  The  energies  in  two  unlike  atoms  are  never  capable  of  exactly  neutralizing 
each  other,  so  that  a  certain  content  of  free  chemical  energy  is  invariably  present  in 
the  atoms  of  every  molecule. 

89 


993  THEORY  OF  ORGANIC  CHEMISTRY. 

nesium  molecule  is  insufficient  to  convert  enough  of  the  bound  energy 
between  the  chlorine  atoms  into  bound  energy  between  metal  and  halo- 
gens, therefore  the  latter  atoms  separate.  On  the  other  hand,  the  greater 
energy  in  the  chlorine  atoms  is  capable  of  using  up  that  in  the  magne- 
sium to  an  extent  that  these  fall  apart.  In  magnesium  chloride,  there- 
fore, the  halogen  has  a  considerably  greater  content  of  free  chemical 
energy  than  it  has  in  sodium  chloride,  and  bound  chemical  energy  exists 
not  only  between  it  and  the  metal,  but  between  the  chlorine  atoms.  We 
may  represent  these  relations  by: 


Mg<^  |  " 


While  the  energy  in  a  molecule  of  magnesium  is  not  sufficient  to 
separate  the  chlorine  atoms,  it  obviously  may  be  able  to  do  so  with  the 
less  negative  oxygen,  and,  if  the  opposite  energies  in  magnesium  and 
oxygen  approximately  neutralize  each  other,  two  molecules  of  magne- 
sium oxide  should  be  formed.  But,  if  we  take  oxygen  and  a  metal  with 
considerably  more  positive  energy  than  magnesium,  say  lithium,  the 
oxygen  is  not  able  to  separate  the  metallic  atoms,  while  the  latter  can 
separate  the  oxygen  atoms,  thus  leading  to  the  formation  of  Li2O,  in  which 
the  Li  atoms  are  held  together  by  bound  chemical  energy.  The  valency 
of  an  element,  according  to  this  interpretation,  represents  the  resultant 
of  the  intramolecular  chemical  forces  acting  on  the  atom  in  terms  of 
bound  chemical  energy,  whether  the  action  takes  place  directly,  that  is 
through  direct  union  of  the  atoms  or  through  space;  or  indirectly,  that 
is,  through  other  atoms.  In  as  far  as  the  free  chemical  energy  in  the 
atoms  is  not  so  converted  into  bound  chemical  energy,  it  will  be  able  to 
exert  readily  a  chemical  attraction  for  such  other  atoms,  either  in  the 
same  or  other  molecules,  for  which  it  shows  a  chemical  affinity. 

Although  a  spontaneous  chemical  change  can  proceed  only  with  in- 
crease of  entropy,  the  increment  depends  on  free  chemical  energy  and 
chemical  affinity  existing  between  those  atoms,  which  in  the  reaction 
enter  into  direct  union  with  each  other.  The  atoms  in  a  molecule  are 
held  together  solely  by  bound  chemical  energy  and,  if  their  chemical  nature 
is  such  that  their  free  chemical  energy  has  very  largely  disappeared  in 
the  formation  of  the  molecule,  the  substance  must  be  chemically  inert; 
if  not,  it  will  be  more  or  less  chemically  active.  Thus,  the  well  neutral- 
ized condition  of  NaCl  and  A12O3,  the  superabundant  positive  energy 
in  Na2O,  and  the  negative  in  A1C13,  is  reflected  in  the  properties  of  those 
substances. 

Let  us  suppose  that  we  could  isolate  and  experiment  with  ele- 
ments other  than  the  noble  gases  in  atomic  condition,  and  could  pre- 
vent the  formation  of  molecules  by  the  union  of  like,  but  not  unlike, 
atoms.  In  such  a  system  free  chemical  energy  would  be  amply  present 

90 


ORGANIC    AND   BIOLOGICAL.  994 

and  chemical  union  would  therefore  depend  alone  on  the  affinity  relations 
of  the  atoms.  Moreover,  if  an  isomeric  substance  could  be  formed,  it 
would  be  that  particular  isomer  which  would  represent  the  maximum 
entropy  of  the  system  under  the  prevailing  conditions. 

For  instance,  the  present  structure  theory  indicates  the  existence  of 
two  isomeric  cyanogen  chlorides,  i.  e.,  C1NC  and  C1CN,  but  leaves  us 
entirely  in  doubt  why  only  one  is  known.  So  great  is  the  uncertainty 
in  regard  to  its  constitution  that  this  has  long  been  a  subject  of  active 
discussion  and  investigation.1  Chlorine,  nitrogen  and  carbon  in  atomic 
condition  would  possess  ample  free  chemical  energy  for  union  and  the 
question  which  isomer  would  be  formed  would  depend  on  the  increase  of 
entropy  connected  with  the  affinity  relations  of  Cl  for  N  and  for  C.  Since 
we  know  that  the  affinity  between  Cl  and  N  is  exceedingly  slight,  and 
that  between  Cl  and  C  is  large,  it  is  absolutely  certain  that  the  isomer 
in  which  the  halogen  is  united  directly  to  the  C,  i.  e.,  C1CN,  would  be  the 
direct  product.  Furthermore,  a  consideration  of  the  energetic  condi- 
tions enables  us  to  predict  the  properties  of  the  isomeric  form  (C1NC) ; 
it  could  exist  only  at  a  very  low  temperature  and  under  ordinary  condi- 
tion the  rearrangement  C1NC — >-ClCN  would  occur  so  quickly,  and 
with  such  a  great  increase  of  heat  that  the  substance  would  be  a  violent 
explosive.2  The  matter  we  actually  deal  with  is,  however,  in  a  molecular 
condition  and  all  chemical  changes  that  do  not  proceed  solely  through 
expenditure  of  free  chemical  energy  involve  an  expenditure  of  energy 
due  to  overcoming  bound  chemical  energy  between  atoms  in  the  molecule. 
Chemical  action  is  dependent,  therefore,  on  a  third  factor,  which  con- 
stitutes a  chemical  hindrance,  and  it  can  proceed  spontaneously  only 
when  the  increase  of  entropy  due  to  changes  of  free  chemical  energy 
and  affinity  is  greater  than  the  expenditure  of  energy  necessary  to  over- 
come the  chemical  hindrance.  That  is,  when  the  value  of  the  equation : 
chemical  affinity  plus  free  chemical  energy  divided  by  chemical  hin- 
drance, is  positive. 

To  ascertain  quantitative  values  for  the  various  factors  that  determine 
an  organic  reaction  is  at  present  impossible,  but  it  is  of  the  greatest  im- 
portance for  the  development  of  organic  theory  to  be  able  to  connect 

1  See  Michael  and  Hibbert,  Ann.,  364,  69. 

2  It  is  evident  that  the  content  of  free  chemical  energy  in  C1NC  would  be  vastly 
greater  than  that  in  C1CN,  which  implies  a  better  condition  of  intramolecular  neutral- 
ization of  the  chemical  forces  of  the  atoms  in  the  latter  structure.     Since  such  chem- 
ical neutralization   proceeds  with  increase  of  entropy,   we  may  substitute  chemical 
neutralization  in  the  place  of  entropy  in  the  second  law  of  thermodynamics.     Further, 
we  may  apply  the  Carnot  principle  to  the  activity  of  free  chemical  energy  of  unlike 
kinds,  and  conclude  that  the  increase  of  entropy  will  be  greatest  when  the  chemical 
forces  are  able  to  neutralize  each  other  exactly.     This  law  of  chemical  neutralization 
has  the  advantage  over  that  of   entropy  in   a   much   wider   application    to   organic 
reactions  (Michael,  /.  prakt.  Chem.,  [2]  60,  293;  68,  489.     Ber.,  38,  23). 

91 


995  THEORY  OF  ORGANIC  CHEMISTRY. 

changes  in  these  values  with  modifications  in  structure.  This  done,  we 
shall  then  be  able  to  predict  relative  changes  in  the  factors  that  contribute 
to  the  entropy  values  and  thus  be  able  to  understand  and  explain  or- 
ganic reactions  to  a  degree  at  present  impossible. 

What  are  the  properties  of  carbon  on  which  the  existence  of  this  won- 
derful and  intricate  organic  world  mainly  depend?  First,  its  capacity 
to  polymerize,  to  form  stable  chains  of  astonishing  length;  second,  the 
extreme  sensitiveness  of  its  properties  to  the  influence  of  other  elements,1 
which  is  shared  in  a  1  ke  degree  only  by  hydrogen,  and  which  has  been 
called  its  "chemical  plasticity";2  and  third,  its  high  valence  combined 
with  its  marked  affinity  for  hydrogen  and  for  most  of  the  non-metals, 
to  form  more  or  less  stable  derivatives. 

The  first  of  these  properties  stands  clearly  in  a  close  relation  to  the 
position  of  the  element  in  the  periodic  system.  In  the  halogen  group, 
the  tendency  to  form  greater  than  diatomic  molecules  is  not  shown, 
with  the  exception  perhaps  of  iodine;  in  the  oxygen  group  it  is  shown 
by  that  element,  but  in  a  far  greater  degree  by  the  other  members.  From 
analogy,  a  similar  tendency  to  form  large  molecules  by  conversion  of 
free  into  bound  chemical  energy  should  be  expected  in  passing  from  oxy- 
gen to  nitrogen,  but  the  latter  element  acts  anomalously,  although  in 
the  formation  of  its  diatomic  molecule  its  free  is  converted  into  bound 
chemical  energy  to  a  remarkable  extent. 

The  next  member  of  this  group,  phosphorus,  shows  a  marked  capacity 
to  polymerize  to  large  molecules,  and  the  conversion  of  ordinary  into 
red  phosphorus,  which  is  accompanied  by  the  evolution  of  only  19  calories, 
is  one  of  the  most  salient  illustrations  in  chemistry  of  how  a  change  of 
free  into  bound  chemical  energy  will  radically  change  the  properties  of 
a  substance.  The  very  existence  of  organic  life  depends  on  carbon  not 
sharing  with  nitrogen  the  property  of  polymerizing  to  a  diatomic  mole- 
cule, which  is  poor  in  free  chemical  energy.  The  actual  change  in  pass- 
ing from  N  to  C  is  similar  to  that  in  going  from  N  to  P,  but  it  is  in  a  de- 
gree much  more  highly  developed,  and  carbon  represents  among  elements 
the  greatest  capability  to  use  the  free  chemical  energy  in  its  atom  to  form 
molecules  containing  a  large  number  of  atoms.  The  midway  position 
of  carbon  in  the  second  series  of  the  periodic  system  indicates  that  there 
is  an  approximate  balance  of  positive  and  negative  corpuscles  in  the 
make-up  of  its  atom.  And,  as  the  polymerizing  capacity  of  non-metallic 
atoms  increases,  generally  speaking,  with  a  tendency  toward  this  con- 
stitution of  their  atoms,  it  seems  reasonable  to  connect  this  all-impor- 
tant property  of  the  carbon  atom  with  its  corpuscular  composition. 

A  relation  which  is  hardly  less  important  for  organic  theory  than  the 

1  Van't  Hoff,  Ansichten  iiber  organische  Chem.,  I,  280;  II,  242. 

2  Michael,  /.  prakt.  Chem.  [2],  60,  325. 

92 


ORGANIC   AND   BIOLOGICAL,.  996 

foregoing,  is  to  what  extent  the  polymerizing  power  of  carbon  is  modified 
by  the  presence  of  other  elements  in  the  molecule,  and  the  influence 
which  they  exert  on  the  affin  ty  of  carbon  for  hydrogen  and  for  non- 
metals.  Without  exception,  every  element  joined  to  carbon  decreases 
its  polymerizing  capacity,  i.  e.,  its  affinity  for  itself,  and  the  influence 
is  in  the  order,  H,  halogen,  N,  S  and  O.  To  the  influence  of  the  last  ele- 
ment carbon  is  so  exceedingly  sensitive  that,  through  direct  union  with 
a  single  atom  of  oxygen,  the  enormous  combining  capacity  of  the  carbon 
atom  for  itself  is  completely  destroyed. 

Notwithstanding  the  considerable  content  of  free  chemical  energy  in 
the  atoms  of  CO,  this  substance  shows  practically  no  tendency  to  polym- 
erize, but  the  characteristic  property  of  carbon  reappears  at  once, 
when  the  influence  of  oxygen  is  neutralized  by  the  presence  of  other  ele- 
ments. Thus,  the  action  of  potassium  on  CO  leads  not  to  COK,  but  to  a 
polymerized  product,  derived  from  benzene. 

Not  only  does  O  decrease  the  affinity  of  C  for  C,  but  of  C  for  H  and  for 
any  non-metal  to  which  carbon  may  be  joined,  whether  the  atoms  are 
directly  or  indirectly  oined.  This  is  true  to  a  degree  directly  propor- 
tionate to  the  extent  of  such  negative  influences  acting  on  the  atoms.1 
The  capacity  of  hydrogen  to  decrease  the  affinity  of  carbon  for  carbon 
is  far  less  than  that  of  oxygen,  but  it  plays,  nevertheless,  an  important 
role  in  many  organic  reactions.  Thus,  the  pinacone — >-pinaco- 
line  rearrangement :  (H3C)2  =  C(OH)  —  (HO)C  =  (CH3)2  — >  (CH3)3= 
C — CO — CH3  +  H2O,  takes  place  on  boiling  with  dilute  mineral  acid,  and  the 

1  Michael,  /.  prakt.  Chem.,  37,  473;  60,  286.  Ber.,  38,  28,  3221.  The  writer  is 
unaware  of  any  facts  in  organic  chemistry  which  are  not  strictly  in  accordance  with 
the  above  stated  rule.  W.  A.  Noyes  (Tins  JOURNAL,  31,  1371)  believes  that  the 
greater  instability  of  acetoacetic  acid  (CH3COCH2CO2H)  over  pyrotartaric  acid 
(CH3COCO2H)  "is  some  slight  indication  that  the  separation  of  the  carbon  atoms 
is  ionic  in  character,  taking  place  more  readily  when  there  is  a  greater  contrast  be- 
tween the  atoms  united  together."  In  the  first-named  acid,  the  group  C — CO2H  is 
under  the  influence  of  H2  and  a  negative,  acidic  radical  (CH3CO),  in  the  second  under 
a  positive  radical  (CH3)  and  O  and  it  is  quite  in  agreement  with  the  above  rule  that 
acetoacetic  acid  splits  off  CO2  much  more  readily  than  pyrotartaric  acid.  The  writer, 
also,  knows  of  no  satisfactory  evidence  in  favor  of  the  view  that  any  strictly  organic 
reaction  is  ionic  in  character  (see  Michael,  Ber.,  38,  29;  Am.  Chem.  J.,  43,  322;  Michael 
and  Hibbert,  Ber.,  31,  1090);  or  of  any  facts  that  are  more  easily  understood  than 
otherwise  by  such  an  assumption.  The  formation  of  ethyl  chloride  from  ethyl  alcohol 
and  phosphorus  pentachloride,  while  phenol  gives  partly  chlorobenzene,  partly  phenyl 
phosphate,  is  mentioned  by  Noyes  (loc.  tit.,  1370)  as  confirming  this  view.  However, 
when  we  consider  that  the  chemical  hindrance  to  the  formation  of  a  chloride,  i.  e., 
the  energy  necessary  to  separate  hydroxyl  from  the  hydrocarbon  radical,  is  much 
greater  with  phenol  than  with  ethyl  alcohol,  it  is  obvious  that  such  assumptions  as 
that  phenol  can  ionize  to  the  phenyl  and  hydroxyl  group,  and  that  ethyl  alcohol 
can  ionize  to  ethyl  and  hydroxyl,  do  not  contribute  in  any  way  to  make  the  subject 
more  clear. 

93 


997  THEORY  OF  ORGANIC  CHEMISTRY. 

reaction  apparently  should  lead,  with  loss  of  water,  to  the  formation  of 
tetramethylethylene  oxide. 

This  compound  contains  a  three-membered,  cyclic  chain,  which  is 
formed  under  considerable  tension,  and,  besides,  a  large  number  (12) 
of  hydrogen  atoms,  exerting  in  a  very  important  position  (3)  their  posi- 
tive influence  on  the  cyclic  carbons.  Such  a  structure  cannot  represent 
a  very  stable  substance.  On  the  one  hand,  there  is  considerable  tension, 
representing  energy  in  a  potential  condition;  on  the  other,  an  extremely 
insufficient,  intramolecular  chemical  neutralization  of  the  positive  by 
the  negative  energy  in  its  atoms.  The  compound  may,  indeed,  be  com- 
pared to  sodium  oxide,  and  shares  with  that  substance  a  capacity  to 
unite  with  water,  most  energetically,  and  with  great  increase  of  entropy. 
It  is  apparent  that  the  oxide  cannot  possibly  be  formed  from  pinacone 
under  the  conditions  of  the  reaction,  but,  if  a  rearrangement  may  lead 
to  the  formation  of  an  intramolecularly  well  neutralized  substance,  this 
may  be  formed,  provided  the  increase  of  entropy  due  to  the  intramol- 
ecular neutralization  is  greater  than  the  decrease  that  is  due  to  the 
chemical  hindrance,  *.  e,,  the  energy  necessary  to  effect  the  migration  of 
a  methyl  group.  These  conditions  are  possible,  for  pinacoline  repre- 
sents a  fairly  well  neutralized  structure  and  has,  consequently,  a  con- 
siderable heat  of  formation;1  and  the  expenditure  of  energy  accompany- 
ing the  migration  of  a  methyl  in  pinacone  is  comparatively  small,  owing 
to  the  decrease  of  the  affinity  of  carbon  for  carbon  by  the  influence  of  the 
numerous  hydrogens. 

That  phenyl  exerts  an  extremely  strong  positive  influence  on  any  atom 
joined  directly  to  it2  is  evident  from  the  fact  that  two  such  groups  united 
directly  with  iodine,  give  that  non-metal  a  metallic  character.  It  might, 
therefore,  have  been  expected,  that  the  accumulation  of  phenyl  groups 
would  facilitate  rearrangements  of  the  nature  of  the  pinacone  — >  pina- 
coline reaction,  as  this  has  been  especially  proven  by  the  investigations 
of  Tiffeneau.  We  have,  moreover,  direct  experimental  evidence  that 
hydrogen  diminishes  the  affinity  of  carbon  for  carbon  hi  the  observa- 
tion of  Acree,3  that  in  the  rearrangement  with  di-/j-tolyldiphenylpinacone 
it  is  the  more  positive  tolyl  radical  that  migrates. 

Another  interesting  illustration  of  this  influence  of  hydrogen  is  found 
in  that  much-discussed  substance  "triphenylmethyl"  (hexaphenyl- 
ethane).  Tshitshibabin4  has  shown  that  replacement  of  five  of  the 
hydrogens  in  ethane  by  phenyl  groups  materially  lessens  the  affinity 
of  the  ethane  carbon  atoms  for  each  other.  It  is,  therefore,  not  surpris- 

1  Zoubuff,  Chem.  Centralbl.t  99,  I,  516. 

2  Michael  and  Leigh  ton,  Ber.,  39,  2792. 
8  Am.  Chem.  J.,  33,  180. 

4  Ber.,  40,  367. 

94 


ORGANIC  AND  BIOLOGICAL.  998 

ing  that  when  the  remaining  hydrogen  is  likewise  replaced,  the  mutual 
affinity  of  these  carbons  is  so  greatly  diminished  that  the  substance 
easily  dissociates  into  two  molecules  of  triphenylmethyl,1  and  that  these 
carbons,  or  the.  carbon,  in  "triphenylmethyl"  joined  to  the  three  phenyl 
groups,  have  chemical  properties  similar  to  those  of  a  very  positive  metal, 
for  instance,  sodium.2  Nor  is  it  surprising  that  hexaphenylethane  may 
undergo  easily  a  desmotropic  rearrangement  into  the  quinoid  form  : 

' 


- 

(C6H5)2=C=<        X 

—  'N 


or,  since  the  difference  in  the  entropy  values  of  these  two  forms  is  slight, 
that  the  existence  of  one  or  the  other  form,  or  a  derivative,  will  depend 
on  the  nature  of  a  reagent  or  even  of  a  solvent.8 

The  remaining  fundamental  properties  of  carbon,  its  high  valency 
and  its  capability  to  combine  not  only  with  hydrogen  but  with  most  of 
the  non-metals  to  form  stable  derivatives,  are  also  related  to  the  posi- 
tion of  the  element  in  the  periodic  system.  An  element  acts  as  mono- 
valent  towards  H,  or  Cl,  when  its  energy  suffices  to  neutralize  that  of  H, 
or  Cl,  to  an  extent  that  the  system  is  incapable  of  uniting  with  further 

1  Since  the  above  was  written  Schlenk  (Ann.,  372,  i)  has  shown  that  with  a  more 
positive  radical  than  phenyl,  i.  e.,  biphenyl,  the  affinity  of  carbon  for  carbon  is  reduced 
to  such  an  extent  that  tribiphenylmethyl  exists  in  solution  in  mono-molecular 
condition,  which  is  a  further  confirmation  of  the  above  explanation. 

1  Michael,  /.  prakt.  Chem.,  [2]  60,  423,  428;  64,  107;  Ber.,  39,  2791. 

'Michael  and  Hibbert,  Ber.,  41,  1091.  A  thermochemical  investigation  on 
intramolecular  rearrangement  will  be  published  later;  it  may  be  stated  that 
all  our  present  experimental  data  on  this  subject  confirm  the  view  that  the 
fundamental  reason  of  the  phenomenon  is  the  increase  of  entropy  proceeding 
with  the  change.  In  intramolecular  changes  it  is  the  formation  of  an  iso- 
mer  with  a  greater  heat  of  formation  and  in  intermolecular  rearrangements 
the  increase  of  entropy  is  connected  with  a  change  in  composition  and  the  reagent 
uniting  with  a  product  of  decomposition;  in  either  case,  slight  chemical  or  physical 
forces  may  bring  about  the  change,  if  the  chemical  hindrance  is  inconsiderable  (see 
Michael  and  Hibbert,  Ber.,  41,  1091).  The  rearrangements  of  camphor  on  treatment 
with  P.p4  and  H2SO4,  to  which  W.  A.  Noyes  (Tnis  JOURNAL,  31,  1372)  recently  called 
attention,  may  be  understood  from  the  point  of  view  here  presented.  In  camphor 
the  affinity  of  the  central  carbon  to  those  with  which  it  is  directly  joined  has  been  di- 
minished considerably  by  the  influence  of  hydrocarbon  radicals  and  the  central  ring 
appears  to  exist  in  a  condition  of  tension;  moreover,  such  reduced  benzene  derivatives 
show  a  tendency  to  pass  over  into  benzene  derivatives,  as  the  formation  of  the  para- 
bonds  in  benzene  is  connected  with  a  considerable  increase  of  entropy  (Michael,  /. 
prakt.  Chem.,  [2]  79,  418).  Phosphoric  anhydride  is  a  powerful  dehydrating  agent 
and  the  formation  of  a  benzene  derivative  (cymene)  with  the  elimination  of  water 
and  rupture  of  a  central  carbon  bond  represents  the  maximum  increase  of  entropy. 
In  its  action  on  camphor  sulphuric  acid  acts  not  only  as  a  hydrolyzing,  but  also  as  an 
oxidizing  agent;  the  formation  of  />-acetyl-o-xylene  undoubtedly  represents  the  max- 
imum entropy  under  such  conditioms. 

95 


999  THEORY  OF  ORGANIC  CHEMISTRY. 

atoms  of  these  elements.  In  passing  from  F  to  O,  from  O  to  N,  and  from 
N  to  C,  the  valency  for  H,  or  Cl,  increases,  because  the  amount  of  energy 
in  these  atoms,  able  to  neutralize  that  of  H,  or  Cl,  is  successively  de- 
creasing. CH4  or  CC14  represent  stable  substances,  because  the  energy 
and  affinity  relations  between  C  and  H,  or  Cl,  are  such  that,  in  the  com- 
bination of  four  atoms  of  hydrogen  or  chlorine  among  themselves  and 
with  one  atom  of  carbon,  comparatively  little  free  chemical  energy  re- 
mains in  any  of  the  atoms.1 

Like  the  polymerizing  capacity  and  the  "chemical  plasticity"  of  car- 
bon, its  power  to  unite  not  only  with  hydrogen,  but  with  most  non- 
metals,  is  due  to  the  approximate  balance  of  the  positive  and  negative 
corpuscular  energies  in  its  atom.  The  direction  in  which  the  affinity  of 
carbon  for  such  elements  will  vary  under  the  influence  of  other  atoms 
in  the  molecule  must  be  toward  those  of  elements  adjacent  to  it  in  the 
periodic  system.  Thus,  the  effect  of  increasing  the  influence  of  H  on  C 
in  relation  to  H,  or  to  a  non-metal,  joined  to  it,  must  be  to  shift  its  affinity 
values  toward  those  of  silicon,  i.  e.,  there  should  be  a  decrease  in  the 
value  for  H  and  an  increase  for  that  of  a  non-metal.  On  the  other  hand, 
increasing  the  influence  of  O  should  shift  them  towards  those  of  N,  i.  e., 
decrease  the  values  both  for  H  and  a  non-metal.  Further,  the  effect  of 
such  changes  on  the  content  of  free  chemical  energy  of  C,  and  of  any 
atom  joined  to  it,  must  stand  in  a  direct  relation  to  the  changes  in  the 
affinity  values;  in  fact,  the  free  must  respond  to  such  changes  before  the 
bound  chemical  energy. 

According  to  van't  Hoff,2  two  atoms  in  a  molecule  acting  through  di- 
rect union  or  through  space,  or  indirectly,  that  is  through  intermediate 
atoms.  This  idea  has  been  further  developed3  and  shown  to  be  of  great 
importance  in  explaining  organic  reactions.  If  we  number  a  certain 
atom  in  any  fatty  compound  with  a  normal  carbon  chain  by  the  figure  i, 
our  present  knowledge  of  the  combined  mutual  influence  between  this 
atom  and  others  in  the  molecule  is  expressed  by  the  following  "scale  of 
combined  influence,"  the  numbers  indicating  the  degree  of  removal  and  the 
extent  of  the  influence  decreasing  in  the  order  given :  2 — 3 — 5 — 6 — 4 — 7 — 

1  Replacement  of  an  H  in  CH4  by  Na  gives  a  substance  with  preponderance  of 
positive  energy,  and  which  is,  therefore,  poorly  neutralized  intramolecularly.     Car- 
bon, a  weak  non-metal,  in  uniting  with  very  positive  metals,  tends  to  form  compounds 
of  the  type  C2Me,  in  which  the  accumulated  negative  energy  of  several  carbon  atoms 
endeavors  to  neutralize  the  positive  energy  of  the  metal.     Only  with  a  weak  positive 
metal  like  Al  are  metallic  derivatives  of  methane  formed,  and  it  is  doubtless  owing 
to  this  relation  between  the  energies  of  C  and  Al,  the  compounds  of  which  are  so  widely 
distributed  in  nature,  that  we  owe  the  occurrence  of  such  enormous  deposits  of  satura- 
ted hydrocarbons. 

2  Ansichten  tieber  die  organische  Chemie,  I,  284-285;  II,  252-254. 

•Michael,  /.  prakt.   Chem.,   [2]  60,  331.     Ber.,  39,   2138-2157,   2780-2790;  40, 
141. 

96 


ORGANIC  AND   BIOLOGICAL.  IOOO 

(9 — 10 — n) — 8.  It  is  to  be  strongly  emphasized  that  the  effect  of  an 
atom  in  position  2  or  3  is  far  greater  than  that  of  any  similar  atom  less 
closely  connected,  and,  in  the  case  of  atoms  farther  removed,  the  in- 
fluence must  be  largely  direct,  i.  e.,  spatial. 

The  principles  developed  above  form  a  new  basis  for  the  theory  of 
organic  chemistry  and  may  be  applied  to  any  problem  arising  in  the 
science. 

Several  important  organic  questions  will  be  discussed  from  the  new 
point  of  view.  One  of  the  weakest  sides  of  the  present  structure  theory 
is  that  it  indicates  the  existence  of  a  countless  number  of  compounds, 
which  are  incapable  of  existence.  One  instance,  that  of  an  isomeric 
chloride  of  cyanogen  (C1NC)  has  been  already  discussed,  but  this  ques- 
tion is  of  such  importance  that  it  will  be  considered  with  substances  of 
a  different  type.  Nitrosomethane  (H3CNO)  does  not  exist,  as  it  passes 
over  spontaneously  into  the  isomeric  oxime:  H3C — NO  — >•  H2C= 
N(OH).  If  we  add  an  oxygen  to  the  nitroso  group,  we  obtain  nitro- 
methane  (H3CNO2),  which  is  perfectly  stable,  but  the  tautomeric  form  of 
which  (H2C  =  NO(OH))  is  so  unstable,  that  its  existence  can  be  proven 
only  by  indirect  means.  The  thermochemical  equation,  2  NO  4-  O2  = 
2NO2  +  26.9  cal.  proves  conclusively  that  the  nitroso  group  contains 
much  more  free  chemical  energy  than  the  nitro,  which  is  the  reason  why 
the  nitroso  group  in  nitrosobenzene  is  so  much  more  reactive  than  the 
nitro  group  in  nitrobenzene.  In  nitrosomethane,  then,  the  following 
energetic  and  affinity  relations  exist:  the  oxygen  has  much  free  chem- 
ical energy  and  a  strong  affinity  for  the  H  of  the  methyl  group,  and  by 
the  change  into  the  oxime,  the  great  content  of  free  chemical  energy  in 
the  nitroso  group  is  largely  converted  into  bound  chemical  energy  and 
heat.  The  transformation  therefore  proceeds  with  increase  of  entropy 
and  the  oxime  represents  an  intramolecularly  well  neutralized  structure, 
which  agrees  with  its  amphoteric  properties  and  the  slight  additive  capacity 
at  the  double  bond.  Since  the  nitro  group  in  nitromethane  has  less  free 
chemical  energy  than  the  nitroso  in  nitrosomethane,  its  oxygen  has  less 
capability  to  overcome  the  bound  chemical  energy  holding  the  hydrogen 
to  the  carbon.  A  rearrangement  to  isonitromethane  is  barred  for  a  sec- 
ond reason,  viz.,  that  it  would  proceed  with  a  degradation  of  entropy, 
for  it  is  evident  that  the  neutral  nitromethane,  the  nitro  group  of  which 
carries  but  little  free  chemical  energy,  is  vastly  poorer  in  such  energy 
than  the  strongly  acidic,  unstaturated  isonitromethane.1 

In  order  that  a  rearrangement  should  proceed  spontaneously,  the  atom 

which  receives  the  migrating  atom,  or  group,  must  have  sufficient  affinity 

for  it  to  be  able  to  overcome  the  bound  chemical  energy  between  the 

migrating  atom,  or  group,  and  the  atom  to  which  it  is  already  joined. 

1  See  Ann.,  363,  21. 

97 


100 1  THEORY  OF  ORGANIC   CHEMISTRY- 

If  we  increase  through  a  structural  change  the  bound  chemical  energy 
more  than  we  do  the  affinity  and  free  chemical  energy  factor;  or  if 
we  decrease  the  latter  without  essentially  altering  the  former, 
we  obviously  increase  the  relative  stability  of  the  new  derivative  and 
it  may  show  an  existence  in  a  free  state.  Through  certain  structural 
changes  the  difference  between  the  entropy  values  of  the  isomeric  forms 
may  be  lessened,  and  we  may  arrive  in  this  way  to  desmotropic  sub- 
stances, the  energy  relations  of  which  are  so  evenly  balanced  that  the 
existence  of  one  or  the  other  form  may  be  determined  by  a  slight  expen- 
diture of  extraneous  chemical,  or  physical  energy.1 

Before  1887  the  substitution  process  in  organic  chemistry  was  uni- 
versally supposed  to  consist  of  the  direct  replacement  of  an  atom,  or 
group,  by  another.  It  was  then  shown,  by  an  investigation  on  the  con- 
stitution of  acetoacetic  ester  and  its  sodium  derivative,2  that  this  view 
could  be  upheld  no  longer  and  that  apparent  substitution  is  often  the  re- 
sult of  a  combination  of  an  addition  and  elimination  process.  Subse- 
quent researches3  have  shown  that  substitution,  as  represented  by  the 
old  view  is  of  comparatively  rare  occurrence,  and  that  a  rational  inter- 
pretation of  the  process  may  be  based  on  the  entropy  principle.  Thus, 
by  the  use  of  a  metal  like  sodium,  which  has  considerable  free  chemical 
energy  and  a  strong  affinity  for  oxygen,  the  hydrogen  in  CH2  =  NOH 
attached  directly  to  oxygen  may  be  driven  out,  with  the  formation  of 
CH2  =  NONa.4  This  change  is  only  apparently  a  direct  replacement 
of  hydrogen  by  sodium,  for  what  actually  occurs  is,  that  the  energy  and 
affinity  values  of  the  metal  are  such  that  it  is  able  to  overcome  the  bound 
chemical  energy  between  the  oxygen  and  hydrogen  and  that  the  latter 
element  is  driven  out,  not  replaced. 

The  distinction  between  replacing  and  driving  out  may  seem  from  the 
above  instance  to  be  unimportant,  but  it  is  in  reality  of  fundamental 
importance  in  organic  reactions.  Let  us  consider,  for  instance,  the  be- 
havior of  nitromethane  and  hydrocyanic  acid  towards  sodium  from  the 
new  point  of  view!  In  the  system 

1  Michael,  Ann.,  363,  27. 

2  Michael,  /.  prakt.  Chem.  [2],  37,  473. 

8  Michael,  Loc.  cit.,  60,  316.  Ber.,  33,  3739;  34,  4028;  38,  22,  1922-1938,  2083, 
2097,  3218.  Amer.  Chem.  ].,  43,  330. 

*  It  does  not  follow  from  the  formation  of  this  sodium  derivative  that  the  change 

as  represented  by  CH2  =NOH  >  CHZ  =NONa  designates  an  increase  of  entropy; 

indeed,  a  consideration  of  the  well  neutralized,  amphoteric  character  of  the  oxime 
and  the  strong  basic,  easily  hydrolyzed  character  of  the  sodium  derivative,  leaves  no 
doubt  that  the  free  chemical  energy  in  the  latter  is  much  greater  than  in  the  former 
structure.  In  the  reaction  much  of  the  free  chemical  energy  in  sodium  is  converted 
into  bound;  it  is  the  total  change  (2CH2  =NOH  +  Na.,  =  2CH,  =NONa  +  H3) 
that  proceeds  with  increase  of  entropy. 


ORGANIC  AND   BIOLOGICAL.  IOO2 


/° 
HSC-N<  |  +  Na, 

> 


the  metal  may  be  attracted  either  by  the  C  or  the  O,  but  not  only  is  the  free 
chemical  energy  in  the  O  larger  than  that  in  the  C,  but  also  the  chemical 
affinity  for  Na.  Moreover,  according  to  the  law  of  entropy,  the  system 
must  strive  to  realize  the  maximum  condition,  which  will  be  the  formation 
of  a  sodium  derivative,  in  which  the  free  chemical  energy  existing  in  nitro- 
methane  and  in  sodium  is  converted  as  completely  as  possible  into  bound 
chemical  energy  and  heat.  This  condition  is  realized  by  the  direct  union 
of  Na  with  O,  since  then  an  almost  neutral  salt  will  be  formed,  while  the 
derivative  containing  the  metal  joined  directly  to  C  would  be  strongly 
basic  and  have  positive  energy  in  great  excess.  Indeed,  if  such  a  deriva- 
tive as  NaCH2NO2  could  be  obtained  at  a  low  temperature,  it  would  pass 
over  at  ordinary  temperature  spontaneously  and  with  an  enormous  in, 
crease  of  entropy  into  CH2  =  N(ONa)O.1  The  intramolecular  hindrance- 
which  nitromethane  offers  to  attack,  of  the  Na  on  the  O  is  the  energy 
necessary  to  overcome  the  bound  chemical  energy  between  a  hydrogen 
and  the  carbon,  which,  owing  to  the  strong  negative  character  of  the 
nitro  group,  is  very  considerably  less  than  in  methane  and  the  reaction 
therefore  proceeds  readily. 

According  to  the  old  substitution  theory,  the  action  of  Na  on  HCN2 
proceeds  by  the  direct  replacement  of  the  hydrogen  by  the  metal,  form- 
ing NaCN;  according  to  the  new  theory,  the  Na  may  be  attracted  by 
the  C  or  the  N,  and  a  salt  may  be  formed  if  the  metal  is  able  to  overcome 
the  bound  chemical  energy  between  the  H  and  the  C  and  the  reaction 
proceeds  with  an  increase  of  entropy.  The  properties  of  the  cyano  group 
leave  no  doubt  as  to  the  existence  of  considerable  free  chemical  energy 
in  the  C  and  the  N,  and  there  is  also  no  doubt  that  Na  has  a  greater  affinity 
for  N  than  for  C:  furthermore,  N,  being  an  element  with  more  negative 
chemical  energy  than  C,  the  energy  of  the  metal  in  NaNC  is  much  better 
neutralized  than  it  would  be  in  NaCN.  The  energy  and  affinity  condi- 
tions permit,  therefore,  hi  the  direct  formation  of  CH2  =  NO(ONa)  and 
NaNC,  the  maximum  possible  increase  of  entropy,  and  any  other  con- 
ception of  the  structures  of  these  salts,  is  as  inconceivable  from  the  new 
theory,  as  the  older  view  leaves  us  wholly  in  the  dark  in  regard  to  them. 

1  Although  a  "double"  bond  is  usually  an  indication  of  the  accumulation  of  free 
chemical  energy,  its  symbolistic  use  for  this  purpose  would  be  misleading.     The  free 
chemical  energy  in  an  atom  must  vary  with  the  extent  of  intramolecular  neutralization/ 
*'.  e.,   in  CH2  =  NO(ONa)   the  free  chemical  energy  at  C    and    N    is  used  up  indi- 
rectly to  a  very  considerable  extent  in  neutralizing  the  positive  energy  of  the  sodium. 
An  approximate  idea  of  the  free  chemical  energy  in  the  atoms  of  a  molecule  can  usually 
be  formed    by  a  consideration  of  their  chemical  nature,  the  structure  and  the  proper- 
ties of  the  substance. 

2  Michael  and  Hibbert,  Ann.,  364,  64. 

99 


ioo3  THEORY  OF  ORGANIC  CHEMISTRY. 

We  have  seen  that  the  positive  energy  in  sodium  has  been  largely 
converted  into  bound  chemical  energy,  when  the  metal  is  introduced 
into  nitromethane  and  that  neither  at  the  unsaturated  carbon  or  nitrogen 
of  H2C  =  N(ONa)O  is  there  much  free  chemical  energy.  It  follows  from 
these  energy  conditions  that  this  salt  should  not  easily  react  with  a  re- 
agent, unless  the  latter  contains  atoms  with  much  free  chemical  energy 
and  a  large  affinity  value  for  certain  atoms  in  the  salt.  Hence,  sodium 
isonitromethane  is  comparatively  inert  toward  methyl  iodide:  but,  if  we 
make  a  change  hi  the  structure  of  the  salt,  so  that  the  metal  is  less  well 
neutralized,  we  shall  facilitate  the  reaction ;  for,  by  doing  so,  we  increase 
not  only  the  free  chemical  energy  of  the  unsaturated  atoms,  but  the 
difference  between  the  heats  of  formation  of  sodium  iodide  and  the  sodium 
salt,  which  is  one  of  the  largest  factors  in  determining  the  entropy  of 
the  reaction.  The  conditions  for  an  easy  reaction  are  fulfilled,  for  instance, 
in  sodium  acetoacetic  ester  (CH3— CONa  =  CH — COOCsH5),  for  in  this 
derivative  the  positive  energy  of  the  metal  is  very  inadequately  neutral- 
ized by  the  weakly  acidic  organic  radical  to  which  it  is  joined,  and  the 
unequal  balance  between  the  positive  and  negative  chemical  forces  must 
leave  considerable  free  chemical  energy  in  the  unsaturated  atoms.  The 
reaction  may  proceed  in  two  directions: 

CH,— CONa  >  I 

I.                                  ||  I        =  CH3CO-CH(CHS)— COOC7H5  +  Nal. 

H5C2OOC-CH     < CH5 

HSC    Na  >  I 

II.  Ill       s=CH,— C(OCH,)=CH— COQC-Hj-fNat 

H5C,OOC— CH=C— O    •< CHS 

It  is  of  interest  to  analyze  the  energy  and  affinity  relations  of  the  un- 
saturated carbon  joined  directly  to  the  carbethoxyl  group  and  those  of 
the  oxygen  joined  to  sodium,  since  they  determine  the  course  of  the  re- 
action. Sodium  iodide  is  formed  in  either  case,  and,  as  the  heat  of  forma- 
tion of  theC-  is  greater  than  that  of  theO-methyl  derivative,1  its  forma- 
tion represents  the  maximum  entropy  of  the  system.  The  introduction 
of  sodium  into  acetoacetic  ester  (CH3— CO— CH2— COOC^)  has  the 
following  effect  on  the  energy  and  affinity  relations  of  the  carbonyl  oxy- 
gen (in  CO)  and  the  methylene  carbon  (hi  CH2) : 

First,  the  free  chemical  energy  in  the  O  has  been  greatly  decreased 
through  direct  union  with  the  metal,  while  part  of  the  bound  chemical 
energy  of  the  C  (used  before  in  holding  the  eliminated  H)  has  been  con- 
verted into  free;  second,  the  affinity  of  the  O  for  CH3  has  been  greatly 
reduced  by  the  positive  influence  of  the  metal,  which,  on  the  other  hand, 
has  neutralized  the  effect  of  the  two  negative  radicals  (CH3CO  and 
COOCjHj)  and  given  the  unsaturated  a-C  a  large  affinity  value  for  methyl. 
It  is  evident  that  when  we  take  the  entropy,  energy  and  affinity  relations 
1  Experimental  proof  will  be  published  later. 

IOO 


ORGANIC  AND   BIOLOGICAL.  IOO4 

into  consideration,  the  conversion  of  the  O-sodium  salt  into  the  C-methyl 
derivative,  *.  e.,  the  reaction  represented  by  I,  is  not  an  abnormal,  but  a 
perfectly  normal,  reaction,1  as,  indeed  is  every  chemical  change  hi  which 
the  condition  of  maximum  entropy  is  realized. 

Finally,  we  shall  discuss  another  fundamental  organic  process,  that  of 
addition,  from  the  standpoint  of  the  second  law  of  thermodynamics. 

If  we  remove  one  hydrogen  from  two  adjacent  hydrocarbon  groups 
in  propane  a  compound  is  formed  (CH3 — CH  =  CH2)  in  which  part  of 
the  bound  chemical  energy  previously  holding  the  eliminated  hydrogen 
atoms  hi  chemical  union  appears  as  free  chemical  energy  at  the  unsatura- 
ted  C-atoms.2  In  the  addition  of  a  reagent  to  such  a  compound,  the 
free  chemical  energy  of  the  unsaturated  atoms  is  more  or  less  completely 
converted  into  bound  chemical  energy  and  heat,  and  the  second  law  of 
thermodynamics  compels  the  addition  to  take  place  hi  such  a  manner 
that  the  maximum  entropy  will  be  realized,  unless  there  is  some  chemical 
hindrance,  which  prevents  this  attainment  of  the  ultimate  goal  of  free 
chemical  energy. 

The  structure  theory  teaches  us  that  in  the  addition  of  hydrobromic  acid 
to  propene,  two  isomers  (propyl  and  isopropyl  bromide)  may  be  formed,  but 
it  fails  altogether  to  give  us  any  indication  which  of  these  products,  or 
whether  both  of  them,  should  result.  The  chemical  hindrance  hi  this  reac- 
tion is  the  energy  necessary  to  overcome  the  bound  chemical  energy  between 
the  H  and  the  Br  of  HBr  to  the  extent  to  which  it  exists  between  them 
in  the  bromopropane  that  will  be  formed  in  the  addition.3  This  hindrance 
is  obviously  quantitatively  the  same  in  the  formation  of  either  isomer. 
The  maximum  entropy  hi  this  addition  will  be  attained,  therefore,  hi 
the  formation  of  the  isomeric  bromopropane  with  the  greater  heat  of  forma- 
tion. 

Obviously,  it  is  of  great  importance  in  this  and  hi  many  other  organic 
reactions  to  be  able  to  trace  the  relation  between  the  structure  of  iso- 
mers and  their  heat  of  formation.  This  is  enabled  by  the  following 
"  thermochemical  law  of  structure."4  In  isomers  with  normal  chains 
and  which  contain  a  common  negative  radical  as  a  nucleus,  that  isomer 
will  have  the  largest  heat  of  formation,  the  positive  radicals  of  which  to 
the  greatest  extent  are  under  the  influence — direct  and  indirect — of  the 
negative  nucleus.  Thus,  in  propyl  and  isopropyl  bromide  the  common 
negative  nucleus  is  CBr,  which  hi  the  last  compound  is  under  the  direct 
influence  of  two  methyl  groups,  while  in  propyl  bromide  only  one  methyl 
is  directly,  the  other  indirectly,  joined.  The  intramolecular  neutraliza- 

1  Michael,  Ber.,  38,  129. 

1  /.  prakt.  Chem.,  [2]  60,  298. 

*  Michael,  Am.  Chem.  ] .,  43,  333  (foot-note). 

4  Michael,  /.  prakt.  Chem.,  [2]  68,  499;  79,  418;  Ber.,  39,  2140. 

101 


1005  THEORY  OP   ORGANIC   CHEMISTRY. 

tion,  which  finds  an  expression  in  the  heat  of  formation,  is  therefore 
larger  in  the  iso  than  in  the  normal  bromide,  and,  since  the  thermic 
value  of  direct  is  very  much  greater  than  that  of  indirect  chemical 
union,  the  heat  of  formation  of  the  former  compound  is  considerably 
larger  than  that  of  the  latter. 

Not  only  does  the  system,  propene  and  hydrobromic  acid,  realize  its 
maximum  condition  of  entropy  in  the  formation  of  isopropyl  bromide,  but 
the  affinity  relations  at  the  points  of  maximum  concentration  of  the  free 
chemical  energy,  i.  e.,  at  the  unsaturated  carbons,  are  such  as  to  favor  the 
course  of  the  reaction  in  this  direction,  since  the  influence  of  methyl  in 
this  substance  is  positive  to  that  of  hydrogen  in  the  same  position.1  This 
relation  causes  in  propene  a  greater  accumulation  of  positive  energy  at  the 
middle  than  at  the  end  unsaturated  carbon  and  the  middle  carbon  must 
have,  therefore,  the  greater  affinity  for  the  strongly  negative  halogen  of  the 
acid.  It  seems  theoretically  probable  that  this  coincidence  of  affinity  and 
entropy  values  should  lead  exclusively  to  the  formation  of  the  iso  deriva- 
tive, as,  indeed,  it  would  if  chemical  change  depended  solely  on  the  free 
energy  and  the  affinity  values.  When  a  mixture,  containing  an  acid 
with  a  very  large  and  a  very  small  .acidity  constant,  is  brought  together 
with  a  quantity  of  a  strong  base  inadequate  for  complete  neutralization 
of  the  acids  present,  there  is  always  an  appreciable  amount  of  salt  de- 
rived from  the  weak  acid  formed.  The  chemical  force  in  each  acid  en- 
deavors to  its  utmost  capacity  to  contribute  its  share  toward  the  increase 
of  entropy,  which  depends  not  only  on  the  values  of  the  affinity  constants 
but,  although  to  a  very  much  smaller  degree,  on  the  actual  mass,  by  weight, 
of  acid  present. 

If  the  formation  of  normal  propyl  bromide  from  propene  and  hydro- 
bromic acid  proceeds  with  an  increase  of  entropy,  which  it  undoubtedly 
does,  we  have  in  this  addition  reaction  two  chemical  forces,  each  striving 
to  increase  the  entropy,  but,  in  this  case,  the  mass  by  weight  cannot  be 
changed  and  the  struggle  is  between  energies.2  Furthermore,  since 
there  is  no  difference  in  the  chemical  hindrance  to  the  addition  in 
either  direction,  it  is  extremely  probable  that  the  relative  amounts  of 
salts,  or  isomeric  bromides,  formed  will  stand  in  a  direct  relation  to  the 
increase  of  entropy,  and  as  this  is  very  much  greater  with  the  formation 
of  isopropyl  bromide,  it  agrees  with  the  theory  that  the  normal  bromide 
is  formed  only  to  a  very  slight  extent.3 

The  principle  here  involved  was  first  used  by  Thomson4  to  determine 
the  relative  acidity  constants,  and  has  been  called  the  "principle  of 

1  Michael,  /.  prakt.  Chem.,  [2]  60,  332;    Ber.,  39,  2142  (footnote). 

2  There  is  no  practical  difference,  as  matter  from  a  chemical  point  of  view  should 
be  considered  only  as  a  carrier  of  chemical  energy. 

3  Michael  and  Leigh  ton,  /.  prakt.  Chem.,  60,  443. 

4  Pogg.  Ann.,  138,  497. 

102 


ORGANIC  AND   BIOLOGICAL,.  IOO6 

partition";1  it  may  be  applied  to  every  organic  reaction  where  two  or 
more  isomers  may  be  formed.2  Let  us  take,  as  illustrations  of  the  appli- 
cation of  this  principle,  the  addition  of  water  by  means  of  sulphuric  acid 
to  hexine-i  and  -2.  In  hexine-i  (CH3— CH2— CH2— CH2— CEE  CH), 
we  have  practically  the  same  conditions  as  in  propene,  that  is,  the  differ- 
ence between  the  energy  and  affinity  values  of  the  unsaturated  carbons 
are  due  to  the  difference  between  the  direct  influence  of  an  alkyl  group 
and  a  hydrogen;  hexanone-2  (CH3— CH2— CH2— CH2— CO— CH3)  and 
probably  a  very  slight  amount  of  hexanal  (CH3 — CH2 — CH2 — CH2 — 
CH2— CHO)  are  formed.  The  relations  in  hexine-2  (CH3— CH2— CH2 — 
C  EE  C — CH3)  are  quite  different;  the  unsaturated  carbons  are  both  joined 
directly  to  alkyl  groups,  and  the  change  in  their  energy  values  is  due 
not  to  direct,  but  to  indirect,  influences,  which  are  largely  spatial.  This 
relation  must  cause  the  heats  of  formation  of  the  products  that  may 
result,  hexanone-2  and  -3,  to  be  much  nearer  together  than  the  isomers 
that  may  be  formed  in  the  addition  to  hexine-i ;  also  an  approximation 
in  the  energy  and  affinity  values  at  the  unsaturated  carbons. 

According  to  the  "principle  of  partition,"  the  relative  amounts  of 
hexanone-2  and  -3  formed  should  not  fall  very  far  apart.  Moreover, 
we  can  approximately  estimate  the  energy  values  of  the  unsaturated 
carbons  in  relative  terms  by  the  use  of  the  "scale  of  combined  influence" 
mentioned  above.  Applying  this  scale  to  the  relations  in  hexine-2, 
omitting  those  atoms  the  influences  of  which  on  the  unsaturated  carbons 
are  equal,2  or  very  nearly  so,  we  find  that  A^ — C3  (joined  directly  to 
methyl)  is  under  the  influence  of  one  carbon  in  the  4th,  one  hydrogen  in 
the  3rd,  and  three  hydrogens  in  the  5th  position,  and  Ar — C  (joined  di- 
rectly to  butyl)  has  one  carbon  acting  in  the  3rd  and  4  hydrogens  in  the 
4th  position.  Since  atoms  in  the  3rd  and  5th  positions  exert  a  greater 
influence  than  those  in  the  4th,  it  is  obvious  that  the  positive  energy 
at  A^ — C  is  greater  than  that  at  Ar — C,  and  that  a  larger  proportion 
of  that  ketone  should  be  formed,  when  the  negative  part  of  the  addenda 
adds  to  it,  i.  <?.,  hexanone-2.  A  re-investigation4  of  the  reaction  shows 
indeed  that  about  60  per  cent,  of  hexanone-2  to  40  per  cent,  of  -3  are 
formed  in  the  reaction. 

The  present  structure  theory  has  been,  and  always  will  be,  of  inestimable 
service  to  organic  chemistry:  it  has  taught  us,  until  recently,5  the  possi- 
ble number  of  isomers  that  may  exist  of  a  given  formula,  and  it  has  been 
a  guide  in  determining  the  constitution  of  most  of  the  substances  that 

1  Michael,  J.  prakt.  Chem.,   [2]  60,  341-354;    Ber.,  39,  2138-2156,   2569,    2786- 
2795;  40,  140. 

2  See  J.  prakt.  Chem.,  60,  341.     Ber.,  39,  2141. 

*  The  capital  "Delta"  denotes  unsaturation  (Baeyer,  Ann.,  245,  112). 
4  Michael,  Ber.,  39,  2133. 
8  Ber.,  39,  203. 

103 


1007  THEORY  OF  ORGANIC  CHEMISTRY. 

have  been  discovered.  But  its  weakness  and  limitations  are  inherent 
in  its  foundation  on  a  mechanical  conception  of  valency  and  an  almost 
exclusive  theoretical  development  along  similar  lines,  for  surely  in  nature 
there  are  no  forces  more  intimately  and  indissolubly  connected  with 
changes  in  energy  than  the  chemical. 

Largely  for  this  reason,  the  structure  theory  fails  to  offer  explanations 
for  many  of  the  simplest  organic  reactions  and,  for  many  years,  it  has 
failed  in  explaining  and  co-ordinating  with  theory  much  of  the  wonder- 
ful experimental  progress  that  has  been  made  in  the  science. 

It  is  true  that  innumerable  attempts  have  been  made  to  amplify  or 
change  the  idea  of  valency  and  the  structure  theory  so  as  to  remedy 
these  deficiencies,  but  they  have  always  been  along  mechanical  lines  and 
have  led  to  such  impossible  theoretical  conceptions  as  new  brands  of 
valencies,  dissociated  and  partial  valencies,  oxonium  and  carbonium 
theories,  steric  hindrance  due  to  size  of  the  atoms,  etc.,  etc. 

All  the  forces  in  nature,  whether  mechanical  or  chemical,  have  the 
same  goal  in  view,  which  is  the  realization  of  the  maximum  condition  of 
entropy,  and  a  scientific  theory  of  chemistry  must  inevitably  have  this 
law  as  its  basis.  The  present  aim  of  organic  theory  is  not  to  abandon 
the  structure  theory,  but  so  to  broaden  and  develop  it  that  it  becomes  a 
consistent  and  harmonious  part  of  nature. 

NEWTON  CENTRE,  MASS. 


PROGRESS  IN  SYSTEMATIC  QUALITATIVE   ORGANIC    ANALYSIS.1 

BY    S.    P.    MULLIKEN. 

Received  June  29,  1910. 

A  general  procedure  in  organic  qualitative  analysis  that  may  be  trusted 
to  lead  to  the  discovery  of  the  proximate  composition  of  any  unknown 
organic  substance  whatever,  whether  this  be  a  simple  compound  or  a 
mixture,  is  demonstrably  incapable  of  practical  realization.  Before  pro- 
ceeding to  the  discussion  of  the  main  subject  of  this  paper,  it  therefore 
behooves  us  to  pause  for  a  moment  to  note  certain  limits  which  Nature 
seems  to  have  set  against  the  too  curious  advances  of  the  analyst. 

The  most  clearly  insuperable  of  these  limitations  are  associated  with 
high  molecular  weight.  If  a  paraffin  hydrocarbon  of  the  formula  C36H72 
were  to  be  isolated  in  a  state  of  perfect  purity  and  in  large  quantity  from 
some  natural  product,  it  would  be  impossible  to  absolutely  identify  it 
as  a  compound  corresponding  to  any  particular  structural  formula  by 
any  combination  of  methods  of  investigation  now  known,  or  whose 
future  discovery  appears  probable.  Such  a  hydrocarbon  would  not  differ 
by  one  one-hundredth  of  one  per  cent,  in  its  hydrogen  or  its  carbon 
content  from  its  adjoining  homologues,  while  in  chemical  and  physical 
properties  there  would  be  no  measurable  differences  between  it  and 
1  An  address  delivered  at  the  Second  Decennial  Celebration  of  Clark  University, 
Worcester,  Mass.,  Sept.  16,  1909. 

104 


ORGANIC   AND   BIOLOGICAL.  1050 

thousands  of  its  four  million  undiscovered  structural  isomers,  which,  ac- 
cording to  the  calculations  of  Cayley,  are  theoretically  possible.  Indeed, 
in  the  case  of  the  discovery  of  such  a  high  hydrocarbon  by  any  process 
other  than  one  of  simple  synthesis,  no  proof  could  be  contrived  which 
would  show  that  the  substance  might  not  well  be  a  mixture  of  many  iso- 
mers and  neighboring  homologues;  for  all  finite  methods  of  purification 
by  fractional  separation  based  on  differences  in  properties  must  inevita- 
bly fail  when  the  numerical  odds  against  them  are  so  great,  and  we  have 
no  choice  in  such  a  case  but  to  resign  ourselves  with  the  best  grace  pos- 
sible to  an  inevitably  partial  solution  of  our  problem. 

But  without  having  ascended  to  such  an  altitude  in  the  homologous 
scale  as  in  the  instance  just  cited,  it  is  often  necessary  or  expedient  to 
accept  incomplete  answers  in  qualitative  inquiries  because  of  our  thraldom 
to  the  rule  that  unknown  compounds  in  mixtures  cannot  in  general  be 
fully  identified  without  previous  isolation  in  a  state  of  purity.  It  is  for 
this  reason  that  it  is  so  common  a  practice  in  technical  analysis  to  ex- 
press the  quantitative  composition  of  familiar  and  important  products 
in  conventional  or  collective  terms.  L/ong  and  thoroughly  as  the  animal 
fats  have  been  studied,  for  example,  there  is  probably  no  instance  on 
record  of  a  quantitative  examination  of  any  natural  fat  in  which  it  could 
be  safely  claimed  that  the  structural  identity  of  all  its  fatty  acids  contain- 
ing less  than  eighteen  carbon  atoms  had  been  irrefutably  established. 
Nor  would  it  be  surprising  under  the  circumstances  if  such  a  result  were 
never  accomplished. 

Thus  handicapped,  systematic  qualitative  organic  analysis  has  de- 
veloped slowly  when  compared  with  the  simpler  qualitative  analysis  of 
the  inorganic  elements  and  salts.  Yet,  if  we  contrast  the  difficulties  to 
be  overcome  in  constructing  an  orderly  scheme  for  the  separation  and 
identification  of  the  list  of  less  than  one  hundred  elements  with  the  diffi- 
culties to  be  met  in  any  corresponding  scheme  for  the  organic  compounds, 
and  then  recall  what  has  already  been  accomplished  in  overcoming  them, 
and  also  the  imperfections  which  present-day  inorganic  qualitative 
schemes  still  exhibit  when  the  rarer  elements  are  included,  the  organic 
chemist  will  find  little  cause  for  pessimism.  The  greater  part  of  the  con- 
tributions to  organic  qualitative  analysis  have  been  made,  however,  with- 
out much  thought  of  the  part  which  they  might  be  made  to  play  in 
any  comprehensive  scheme  of  procedure,  and  have  often  owed  their 
origin  to  incidental  observations  made  during  the  execution  of  investiga- 
tions of  broader  scope  and  different  purpose.  Fischer's  numerous  char- 
acterizations of  compounds  in  the  sugar,  purine  and  protein  groups,  by 
well  chosen  reactions  and  derivatives,  and  his  ingenious  separations 
for  the  amino  acids  formed  in  proteolysis  are  illustrations  of  this  fact. 
Among  the  rather  numerous  handbooks  of  organic  analysis,  although 

105 


1 05 1  SYSTEMATIC   QUALITATIVE   ORGANIC   ANALYSIS. 

many  devote  much  space  to  qualitative  testing,  the  speaker  recalls  only 
one  whose  author  (Barfoed,  1878)  has  been  sufficiently  venturesome  to 
incorporate  the  phrase  "Organic  Qualitative  Analysis"  in  its  title.  Of 
the  many  commendable  partial  schemes  for  the  isolation  and  identifica- 
tion, or  the  detection  in  certain  classes  of  mixtures,  of  carbon  compounds 
belonging  to  restricted  groups,  we  owe  the  origin  of  a  large  proportion 
to  an  acute  need  of  special  analytical  assistance  in  some  department  of 
industry,  research,  or  governmental  control.  To  such  cause  we  owe 
much  of  what  is  most  valuable  in  Allen's  "  Commercial  Organic  Analysis," 
Post's  " Chemisch-technische  Analyse,"  and  the  works  of  Vortmann, 
Dragendorff,  Hoppe-Seyler,  Konig,  Leach,  Sherman,  and  others.  The 
investigation  of  methods  for  the  detection  and  determination  of  constit- 
uent radicals  has  also  proved  a  fruitful  source  of  valuable  material,  much 
of  which  has  been  made  accessible  for  ready  reference  in  H.  Meyer's 
"Analyse  und  Konstitutionermittelung  organischer  Verbindungen. " 

The  resolution  of  mixtures  is  usually  the  first,  and  often  the  most 
difficult  part  of  a  qualitative  analysis.  Definite  plans  for  correlation 
in  a  broad  general  procedure  of  the  methods  of  separation  that  have 
proved  effective  in  the  study  of  restricted  classes  of  mixtures  have  yet 
to  be  proposed.  The  speaker  is  not  in  accord  with  the  rather  prevalent 
view  that  it  is  useless  to  strive  for  broader  and  more  systematic  separa- 
tion procedures.  But,  on  the  other  hand,  as  he  is  unprepared  to  play 
the  prophet's  role,  it  may  be  more  profitable  for  him  to  confine  the  fol- 
lowing discussion  to  the  topic  of  systematic  procedures  for  the  identifica- 
tion of  pure  compounds,  this  being  an  important  division  of  the  qualita- 
tive problem  whose  solution  seems  nearer  accomplishment. 

Prior  to  1831,  the  date  of  the  inauguration  of  those  revolutionary 
improvements  in  organic  combustion  methods  by  Liebig,  which  rendered 
it  possible  to  determine  the  percentage  composition  of  any  carbon  com- 
pound with  considerable  accuracy  and  comparative  convenience,  it  does 
not  appear  that  any  comprehensive  systematic  methods  for  identifying 
previously  described  organic  compounds  had  been  formulated,  or  that 
the  lack  of  them  had  been  felt  as  a  serious  inconvenience.  The  num- 
ber of  pure  compounds  that  had  been  described  was  comparatively  small, 
the  possibility  of  laboratory  syntheses  for  organic  compounds  having 
only  just  become  recognized,  and  the  descriptions  of  such  compounds 
as  were  known  were  not  scattered  as  to-day  through  an  almost  endless 
list  of  special  journals  and  treatises.  A  chemist  of  this  earlier  period, 
if  a  man  of  extended  practical  experience,  well  read,  and  having  access 
to  a  good  library,  rested  more  or  less  content  in  the  knowledge  that  he 
could  probably  accomplish  by  a  purely  eclectic  procedure,  based  on  his 
miscellaneous  sources  of  information,  ingenuity,  and  common  sense, 
all  that  was  then  analytically  possible. 

1 06 


ORGANIC   AND   BIOLOGICAL.  1052 

Thanks  to  Liebig's  writings  and  the  influence  of  the  students  who  passed 
from  his  Giessen  laboratory,  his  simplified  methods  of  ultimate  analysis 
were  not  long  in  becoming  widely  known.  In  scientific  laboratories 
they  were  everywhere  welcomed  and  adopted.  This  welcome  was  richly 
deserved;  for,  besides  serving  as  a  means  to  determine  percentage  com- 
position values — which  will  perhaps  always  remain  the  most  funda- 
mental of  chemical  constants — their  use,  in  connection  with  the  later 
widely  adopted  vapor  density  molecular  weight  determination  meth- 
ods, furnished  all  information  required  for  the  calculation  of  empirical 
formulas.  These,  if  we  add  knowledge  of  genetic  relations  and  chemical 
behavior,  become  structural  formulas  with  all  the  added  information 
as  to  chemical  characteristics  and  individuality  which  are  inherent  in 
the  latter.  The  vapor  density  molecular  weight  determination  methods 
reached  their  climax  for  the  organic  chemist  in  the  air  displacement 
form  proposed  by  Victor  Meyer  in  1878.  The  prestige  of  the  empirical 
formula  as  an  aid  in  compound  identification  was  soon  still  further  en- 
hanced by  the  discovery  of  Raoult's  principle,  followed  by  the  invention 
of  the  Beckmann  thermometer  in  1888,  these  aids  to  molecular  weight 
determination  finally  enabling  the  inclusion  among  the  compounds  of  di- 
rectly determined  empirical  formulas  of  a  large  share  of  the  non-volatile 
compounds.  Other  causes  about  to  be  mentioned  also  conspired  to  bring 
the  analytical  importance  of  the  empirical  formula  to  extreme  promi- 
nence. 

During  the  two  decades  closing  in  1880,  the  unprecedented  increase  in 
newly  described  organic  compounds  had  already  begun  to  assume 
the  dimensions  of  a  threatening  deluge.  The  synthesis  responsible 
for  the  creation  of  a  new  species,  being  aware  of  its  genetic  relations, 
and  having  determined  its  empirical  formula,  was  usually  in  a  position 
to  correctly  interpret  the  chemical  identity  of  his  progeny;  though 
to  prove  that  his  discovery  was  really  an  original  one  by  a  search 
through  the  swollen  literature  had  become  a  task  to  be  undertaken  with 
fear  and  trembling.  The  time  rapidly  approached  when  the  healthy 
future  development  of  organic  research  seemed  likely  to  receive  a  serious 
check  from  the  confusion  and  discouragement  in  store  for  investigators 
who  could  only  hope  to  escape  plagiarism  in  recounting  their  alleged  dis- 
coveries by  well-nigh  interminable  bibliographical  delvings.  Those  of  us 
in  the  younger  generation  of  organic  chemists  are  not  in  a  position  to  even 
faintly  appreciate  the  sigh  of  relief  that  must  have  been  breathed  by 
hundreds  of  workers  in  many  lands  when  these  chaotic  conditions  were 
ameliorated  in  1882  by  the  completion  of  the  first  edition  of  Friedrick 
Beilstein's  great  handbook  of  organic  chemistry.  With  rare  foresight 
Beilstein  had  in  season  anticipated  the  mission  which  this  remarkable 
work  had  to  fulfil,  and  its  publication  after  twenty  years  of  incessant 


1053  SYSTEMATIC   QUALITATIVE   ORGANIC   ANALYSIS. 

labor,  occurring  as  it  did  at  this  critical  period  in  the  development  of 
organic  chemistry,  is  of  epoch-making  importance  to  organic  qualitative 
analysis  as  well  as  to  all  other  departments  of  the  science. 

Beilstein's  "Handbuch"  was  a  digest  of  the  complete  literature  of  the 
modes  of  formations,  properties  and  reactions  of  all  the  analyzed  com- 
pounds of  carbon.  It  did  not  purport  to  be  an  analytical  guide,  and  in 
its  introduction  the  possibility  of  a  qualitative  organic  analysis  at  all 
comparable  to  the  inorganic  is  categorically  denied.  Nevertheless, 
because  of  the  completeness  and  orderly  arrangement  of  its  concise  de- 
scriptions, its  importance  as  an  aid  in  the  identification  of  organic  com- 
pounds may  be  fairly  estimated  as  greater  than  that  of  all  the  special 
analytical  treatises  which  have  ever  been  issued.  Its  general  classifica- 
tion for  the  compounds  has  sometimes  been  criticized  as  clumsy  and 
confusing,  but  the  division  of  species  according  to  chemical  function, 
saturation,  and  in  homologous  series,  has,  on  the  whole,  served  the  in- 
terests of  the  analyst  well;  and  the  invention  of  a  simple  device  for  loca- 
ting in  its  pages  the  description  of  any  desired  compound  of  known  em- 
pirical formula,  which  has  been  more  recently  made  available  through 
the  ingenuity  and  cooperation  of  M.  M.  Richter,  the  manager  of  the 
Prinz  Dye  Works  in  Carlsruhe,  has  now  long  served  in  case  of  compounds 
of  this  class  to  greatly  facilitate  their  identification. 

Richter's  "Tabellen  der  Kohlenstoff-Verbindungen"  with  its  20,000 
brief  references  to  the  literature  and  properties  of  the  analyzed  organic 
compounds  was  issued  in  1884.  The  first  volume  of  the  second  edition 
appeared  in  1900  under  the  altered  title  of  "Lexikon  der  Kohlenstoff- 
Verbindungen."  In  its  present  completed  form  this  edition  registers 
more  than  one  hundred  thousand  compounds  of  determined  empirical 
formulas,  and  gives  direct  access  to  the  full  description  and  literature  of 
each  by  citation  of  the  proper  volume  and  page  number  of  Beilstein. 
As  a  bibliographical  index  for  compounds  of  known  empirical  formula  it 
is  hard  to  imagine  anything  simpler  or  more  complete  than  the  Rich- 
terian  classification.  The  exact  position  of  every  possible  compound 
(if  we  exclude  the  arrangement  of  isomers  with  reference  to  one  another) 
is  automatically  fixed  by  its  formula  alone,  and  is  as  easily  found,  and 
in  much  the  same  manner,  as  a  word  in  a  dictionary  through  a  knowledge 
of  the  relative  positions  of  its  letters  in  the  alphabet.  The  completeness 
of  the  tabulation  is  suggestively  indicated  by  the  author's  remark  that 
his  guiding  thought  during  its  preparation  was  "  Das  Unwesentliche, 
d.  h.  die  weniger  bekannten  Verbindungen,  stets  in  erster  L,inie  und 
vollstandig  hervorzuheben. "  On  the  other  hand,  its  use  as  the  basis 
for  a  method  of  identification  for  unknown  organic  compounds  is  often 
attended  with  serious  or  prohibitive  difficulties. 

It  has  been  already  pointed  out  that  an  absolute  determination  of 

1 08 


ORGANIC   AND   BIOLOGICAL.  1054 

species  among  the  carbon  compounds  is  theoretically  impossible  by  any 
combination  of  tests  in  the  case  of  compounds  of  extremely  high  molec- 
ular weight,  and  that  the  unavoidable  errors  of  ultimate  organic  analysis 
with  such  substances  are  large  enough  to  prevent  analysts  from  making 
any  selection  between  a  large  number  of  seemingly  possible  and  equally 
probable  empirical  formulas.  This  unfortunate  circumstance  prohibits 
the  use  of  the  Richterian  system  in  large  and  important  fields  where 
quantitative  investigation  by  other  methods  may  be  conducted  with  good 
prospect  of  success.  For  example,  the  dyestuff  tables  of  Schultz  and 
Julius  describe  a  hundred  distinct  tetra-azo  dyestuffs  having  molecular 
weights  above  500,  and  some  of  them  exceeding  1000.  These  colors  are 
many  of  them  important,  their  constitutions  well  established  by  syn- 
thesis, and  their  identification  through  their  physical  and  chemical 
properties,  or  at  least  their  approximate  identification — which  is  often 
all  that  is  required — is  not  especially  troublesome.  The  absurdity  of 
an  attempt  to  identify  an  unknown  color  of  this  class  through  its  em- 
pirical formula — which  would  usually  involve  the  quantitative  deter- 
mination of  at  least  six  elements  with  an  impossible  degree  of  precision — 
is  so  patent  from  the  mere  mention  of  the  stoichiometric  conditions  that 
it  may  be  hoped  it  has  never  been  made  by  any  rational  being. 

A  second  defect  in  the  method  of  the  empirical  formula,  which  in  the 
ordinary  laboratory  curtails  its  actual  application  even  more  than  the 
absolute  limitation  just  mentioned,  is  the  fact  that  much  special 
manipulation,  skill  and  apparatus  are  necessary  to  insure  trustworthy 
results  in  elementary  organic  analysis,  and  that  so  much  time  is  always 
consumed  in  the  preliminary  arrangements  for  a  combustion  and  in  its 
conduct.  In  the  larger  organic  laboratories  where  the  combustion  of 
new  synthetic  products  is  an  almost  daily  incident  of  the  routine  of 
investigation,  and  the  equipment  of  the  combustion  room  is  maintained 
at  all  times  in  a  state  of  perfect  preparedness  for  emergency  calls,  so  that 
no  time  need  ever  be  lost  in  the  mobilization  for  an  analysis,  the  organic 
combustion  is  not  formidable  to  the  initiated.  But  under  other  circum- 
stances— and  they  are  the  prevalent  ones — chemists  do  not  resort  to 
the  method  of  the  empirical  formula  except  under  rather  strong  com- 
pulsion, and  many  identifications  which  ought  to  be  made  are  not  even 
attempted. 

In  view  of  these  defects  and  inconveniences,  it  is  natural  to  inquire 
whether  there  is  hope  of  securing  in  the  future  any  scientific  substitute 
for  the  method  of  the  empirical  formula.  In  the  comprehensiveness 
and  simplicity  of  its  classification  of  compounds,  it  must  be  admitted 
that  it  will  be  vain  to  expect  anything  but  loss  from  radical  changes  in 
the  Richterian  arrangement;  but,  if  we  accept  the  logician's  definition 
of  a  scientific  classification  as  "Nothing  more  than  a  system  of  division 

109 


1055  SYSTEMATIC  QUALITATIVE   ORGANIC   ANALYSIS. 

carried  out  in  such  a  way  as  to  best  serve  a  given  purpose,"  and  if  our 
purpose  is  convenience  and  effectiveness  in  general  qualitative  investiga- 
tion, the  possibility  of  other  and  more  scientific  classifications  is  not  to 
be  denied;  and  it  has  seemed  to  the  speaker  that  the  discovery  of  such 
methods  of  classification  is  at  present  one  of  the  important  and  attractive 
fields  for  organic  chemical  research.  What  the  final  outcome  of  this 
quest  will  be — if  we  have  the  right  to  speak  of  a  final  outcome  in  a  prob- 
lem which  from  its  nature  permits  of  only  progressive  partial  solution 
— no  one  can  as  yet  speak  with  full  authority.  Some  of  the  general 
considerations  bearing  on  the  subject  may,  however,  be  brought  to  your 
attention. 

Scientific  classifications  are  chiefly  concerned  with  relations  of  resem- 
blance and  contrast.  To  answer  the  question  what  points  of  resemblance 
and  contrast  must  be  regarded,  and  in  what  order,  if  we  are  to  make  a 
classification  scientific,  is  to  say  that  no  basis  of  classification  ("  funda- 
mentum  dimsionsis")  is  per  se  better  than  any  other.  All  depends  on 
the  ultimate  object.  If  the  object  of  a  classification  is  ready  diagnosis 
of  natural  objects,  it  is  evident  that  the  characteristics  used  as  differentiae 
for  distinguishing  between  groups  should  permit  of  easy  as  well  as  cer- 
tain determination;  and  it  is  also  a  good  quality  in  such  a  division  to 
collect  individuals  in  the  lowest  group  for  comparison  which  are  on  the 
whole  most  alike.  Methods  of  subdivision  which  aim  at  discovering 
something  without  regard  to  whether  the  resemblances  of  adjacent 
species  are  fundamental  or  accidental,  like  the  classification  of  words  in  a 
dictionary  according  to  the  accidental  alphabetical  sequence  of  their 
letters,  are  called  artificial  systems.  The  Linnaean  and  Richterean 
systems  belong  to  this  category.  No  comprehensive  system  of  division  in 
natural  science  is  free  from  many  artificial  features.  But  these  are  more 
likely  to  be  prominent  in  the  early  than  in  the  later  stages  of  the  develop- 
ment of  a  classification,  the  pioneer  in  such  work  having  to  first  bridge 
his  rivers  with  such  structural  materials  as  lie  nearest  at  hand. 

To  the  observant  mind  the  discovery  of  possible  differentiae  for  the 
classification  of  natural  objects  is  an  easy  and  fascinating  pastime,  though 
to  make  a  wise  selection  may  often  be  quite  the  reverse.  Thus  we  read 
in  the  quaint  diary  of  the  botanist  Linnaeus  under  the  date  of  June  12, 
1632,  in  his  "Lapland  Observations":  "Close  to  the  road  hung  the  under 
jaw  of  a  horse,  having  six  front  teeth,  much  worn  and  blunted,  two  canines, 
and  at  a  distance  from  the  latter  twelve  grinders,  six  on  each  side.  If 
I  knew  how  many  teeth  and  what  peculiar  form,  as  well  as  how  many 
udders,  and  where  situated,  each  animal  has,  I  should  perhaps  be  able 
to  contrive  a  most  natural  methodical  arrangement  of  quadrupeds." 
As  with  Linnaeus'  quadrupeds,  so  with  organic  compounds — we  find  a 
multitude  of  easily  determined  properties  from  which  we  may  choose 

no 


ORGANIC   AND   BIOLOGICAL.  1056 

the  differentiae  for  our  classification,  and  by  the  exact  coincidence  of  a 
sufficient  number  of  these  characteristics  of  different  orders  with  those 
of  an  unknown  compound,  the  identity  of  the  latter  may  be  proved. 
Qualitative  elementary  composition,  color,  melting  and  boiling  point, 
specific  gravity,  odor,  taste,  solubility,  refractive  index,  specific  optical 
rotation,  electrical  conductivity,  absorption  spectra,  color  reactions, 
precipitations,  and  general  chemical  behavior — especially  simple  chemical 
reactions  that  throw  light  on  the  nature  of  dominant  atomic  groups  and 
structural  peculiarities — may  all  be  thus  used. 

Regarding  the  chemical  compound,  or  individual,  as  the  species  of  a 
chemical  system,  it  appears  most  natural  to  group  these  species  in  such  a 
way  as  to  make  the  next  higher  unit  or  genus  contain  species  which  are 
most  similar  in  general  chemical  behavior.  This  would,  for  example, 
tend  to  make  congeners  of  members  of  all  homologous  series  containing 
the  aldehyde  radical,  provided  we  could  find  sufficiently  reliable  and 
simple  chemical  tests  for  showing  the  presence  of  the  CHO  group.  Re- 
cent chemical  literature  abounds  in  suggestions  for  tests  suitable  for 
generic  differentiae,  though  much  additional  work  will  be  required  in 
every  instance  to  determine  the  real  value  and  exact  boundaries  of  the 
genera  that  their  employment  would  create,  there  being  ever-present 
danger  that  overconfidence  in  the  constancy  of  behavior  of  a  reagent 
towards  a  given  radical  in  different  structural  environments  may  lead 
to  false  conclusions.  Thus  it  is  not  safe  to  assume  that  under  certain 
specified  conditions  all  ketones  will  form  oximes;  all  acids  and  phenols 
will  dissolve  in  alkali;  all  esters  will  be  saponified;  or  all  unsaturated 
compounds  will  add  bromine.  In  first  delimiting  a  genus  such  assump- 
tions may  be  adopted,  after  preliminary  experiments,  as  tentative 
working  hypotheses ;  but  the  contents  and  existence  of  the  genus  must  be 
held  to  be  strictly  provisional  and  dependent  on  the  positive  outcome  of 
the  proposed  genetic  reaction  when  applied  to  a  larger  number  of  its  care- 
fully selected  species,  and  to  its  negative  outcome  when  tried  with  numer- 
ous members  of  all  genera  of  higher  numerical  designation  in  the  same 
classificatory  order.  It  will  also  be  the  duty  of  the  classifier  to  indicate, 
in  a  manner  that  will  leave  no  doubt  in  the  minds  of  readers,  all  descrip- 
tions, or  parts  of  descriptions,  for  which  he  is  personally  responsible; 
for  unless  some  means  is  given  for  distinguishing  between  data  which  he 
has  verified,  and  others  which  he  has  not,  the  authority  is  liable  to  be 
more  or  less  implicated  in  the  mistakes  of  others  for  which  he  need  have 
assumed  no  responsibility,  but  which  will  now  tend  to  vitiate  the  value 
of  his  classification  as  a  whole. 

It  would  be  premature  at  this  time  to  present  in  all  its  minutiae  any 
plan  for  such  a  classification  as  has  just  been  suggested  in  its  outlines. 
Details  in  illustration  of  the  speaker's  original  conception  and  partial 

in 


IO57  SYSTEMATIC   QUALITATIVE   ORGANIC   ANALYSIS. 

execution  of  such  a  plan  are  to  be  found  in  the  already  published  first  and 
third  volumes  of  his  "Method  for  the  Identification  of  Pure  Organic  Com- 
pounds." All  that  is  desired  here  is  to  lead  to  a  discussion  of  the  ad- 
vantages in  the  plan  for  Chemistry;  and  if  it  is  sound,  to  arouse  interest 
with  a  view  to  eventually  bringing  about  a  wider  cooperation  for 
furthering  its  future  development.  The  difficulties  to  be  overcome  are 
considerable.  Recorded  descriptions  of  organic  compounds,  while  fre- 
quently very  complete  for  a  few  properties  like  melting  and  boiling 
points,  are  commonly  equally  deficient  concerning  others — especially  in 
exact  data  showing  the  extent  of  the  influence  of  slight  variations  in  chem- 
ical constitution  on  the  results  of  the  selected  differential  tests.  The  occa- 
sion hence  arises  for  an  investigation  or  partial  reexamination  of  a  con- 
siderable proportion  of  the  species  receiving  locations.  If  one  has  the  pure 
compounds  with  which  to  experiment,  the  tests  are  easily  made.  But 
as  only  a  few  thousand  pure  compounds  can  be  procured  through  com- 
mercial channels,  and  most  of  these  require  some  purification,  sucess 
in  the  construction  of  a  comprehensive  diagnostic  classification  implies 
assistance  from  private  collections  throughout  the  world;  for  to  syn- 
thesize any  considerable  part  of  the  rarer  species  would  overtax  the 
facilities  of  the  largest  and  best  equipped  of  laboratories. 

To  bring  a  majority  of  the  carbon  compounds  referred  to  in  Richter's 
Lexikon  into  an  essentially  "natural"  classification  of  the  kind  sug- 
gested would,  assuming  the  study  of  tests  and  revision  of  constants 
to  be  thoroughly  done,  perhaps  involve  a  labor  as  great  as  the  trans- 
formation of  the  "artificial"  botanical  classification  of  Linnaeus  into 
the  modern  "natural"  system  as  it  was  left  by  de  Candolle.  An 
undertaking  of  this  magnitude  and  character  might  presumably  in  the 
present  century  be  accomplished  with  greater  benefit  to  science  under  the 
direction  of  some  such  organization  as  the  committee  entrusted  with  the 
periodical  revision  of  Beilstein's  "Handbuch"  and  the  Richter  "Lexikon" 
than  under  private  auspices. 

MASSACHUSETTS  INSTITUTE  OF  TECHNOLOGY, 
BOSTON,  MASS. 


112 


THE  OUTLOOK  FOR  A  BETTER  CORRELATION   OF   SECONDARY 
SCHOOL  AND  COLLEGE  INSTRUCTION  IN  CHEMISTRY.1 

If  the  question  "Should  more  credit  be  allowed  by  institutions  of  col- 
lege grade  for  work  in  chemistry  done  by  pupils  in  secondary  schools?" 
were  asked  of  any  considerable  number  of  teachers  in  those  schools  it  is 
easy  to  believe  that  the  majority  would  make  an  affirmative  reply,  and 
that  all  would  at  least  be  inclined  to  add  to  the  query  the  traditional 
language  of  the  examination  paper,  "If  not,  why  not?  Give  reasons  for 
your  answer."  Inasmuch  as  the  present  conditions  with  respect  to  the 
correlation  of  the  work  in  the  two  grades  of  schools  is  admittedly  unsatis- 
factory, and  since  these  conditions  are  essentially  determined  by  deci- 
sions on  the  part  of  the  colleges,  it  is  fitting  that  the  situation  should  be 
occasionally  reviewed,  with  the  purpose  of  finding  out,  on  the  one  hand, 
how  far  the  present  situation  can  be  defended  and,  on  the  other  hand, 
of  seeking  means  by  which  better  results  can  be  attained.  Others  have 
dealt  with  this  subject  from  various  standpoints,  and  the  statements 
which  follow  are  made  less  with  the  expectation  that  anything  like  a 
final  word  will  be  said,  than  the  hope  that  a  contribution  of  the  experi- 
ences of  the  teachers  in  one  more  laboratory,  and  a  few  of  the  conclu- 
sions which  they  have  reached,  may  do  something  to  aid  in  the  compre- 
hension of  one  of  the  most  perplexing  problems  which  confront  the  teacher 
of  elementary  chemistry  to-day. 

The  experiences  here  recorded  have  been  gathered  from  the  routine  of 
instruction  in  a  technical  school,  and  it  may  be  considered  doubtful  by 
some  whether  observations  made  in  the  laboratory  of  a  technical  school 
in  which  the  instruction  in  chemistry  becomes  a  part  of  a  "step  up" 
system  of  requirements  (that  is,  one  in  which  successful  work  in  subjects 
of  later  years  is  directly  dependent  upon  a  thorough  grounding  in  earlier 
subjects  to  a  degree  that  does  not  obtain  in  the  less  rigid  sequence  of 
studies  in  the  college)  should  be  taken  as  a  basis  for  conclusions  bearing 
also  upon  college  work;  but,  while  such  doubts  may  be  justified  in  the 
case  of  a  limited  number  of  institutions  in  which  chemical  instruction  is 
merely  a  part  of  a  general  college  course,  it  is  increasingly  true  that  more 
and  more  students  from  all  colleges  are  seeking  the  technical  schools  to 
complete  some  of  the  professional  courses  which  they  offer.  In  the  case 
of  the  university  the  technical  school  may  well  be  a  part  of  its  own  sys- 
tem; in  the  case  of  the  college  it  means  that  its  reputation  for  efficiency 
in  teaching  is  to  be  unexpectedly  tested  by  some  other  group  of  instruc- 
tors, and  it  should  be  as  much  a  matter  of  concern  to  them  to  see  that 
their  students  have  an  adequate  preparation  in  the  sciences  as  to  see 
that  they  are  soundly  taught  in  mathematics  or  the  humanities.  Many 
of  the  colleges  have  much  room  for  improvement  in  this  respect. 

Let  us  first  look  at  the  situation  as  it  apparently  exists  at  present  in 
some  of  our  typical  institutions  as  indicated  by  the  following  brief  sum- 
maries. The  term  "entrance  requirement"  is  assumed  to  represent 
the  work  of  a  year  with  the  ordinary  time  allotment  for  chemistry  in  the 
preparatory  schools.  The  data  have  been  obtained  through  direct  cor- 
respondence with  representatives  of  the  institutions  mentioned. 

1  Presented  at  the  second  decennial  celebration  of  Clark  University,  Worcester, 
Mass.,  September  17,  1909. 


1 .  Yale  College. — Does  not  require  chemistry  for  entrance.     Students 
may  take  an  examination  for  advanced  standing,  but  rarely  do  so. 

2.  Harvard  College. — Those  who  have  passed  the  entrance  requirement 
take  the  same  lecture  as  those  who  have  had  no  chemistry,  but  they  have 
special  laboratory  work  and  more  advanced  instruction  in  a  special  divi- 
sion.    They  are  also  allowed  to  take  a  first  course  in  organic  chemistry 
in  the  freshman  year.     Admission  of  such  students  to  work  in  qualita- 
tive analysis  has  not  proved  successful.     Those'  who  present  more  chem- 
istry than  the  entrance  requirement  are  individually  considered,  but  are 
rarely  excused  from  college  work  on  the  basis  of  secondary  school  work. 

3.  Cornell  University. — The  entrance  requirement  is  nearly  the  same 
as  that  of  the  College  Entrance  Examination  Board,  but  the  passing  of 
this  examination  does  not  secure  credit  for  introductory  inorganic  chem- 
istry in  the  university.     The  student  may  take  an  examination  for  ad- 
vanced standing  if  he  desires. 

4.  Columbia   University. — Those  who  pass  the  College  Entrance  Ex- 
amination Board  examination  are  admitted  to  a  special  course  in  lectures 
in  chemistry,  including  a  somewhat  advanced  treatment  of  the  subject. 

5.  Syracuse  University. — For  one  year  of  chemistry  in  a  normal  school 
credit  is  given  for  elementary  chemistry  in  college,  provided  the  student 
takes  another  course  in  chemistry  and  passes  well.     After  one  year  of 
chemistry  in  a  secondary  school,  pupils  are  allowed  to  take  the  regular 
examination  in  elementary  chemistry,  and  if  they  pass,  credit  is  given 
for  that  course.     If  chemistry  is  accepted  for  admission  the  student  is 
admitted  to  second-year  classes,  but  no  credit  is  given  for  elementary 
chemistry. 

6.  Washington  and  Lee  University. — Students  from  secondary  schools 
with  the  equivalent  of  Remsen's  "Briefer  Course"  are  admitted  to  a 
course   including   physico-chemical    topics   and    to   qualitative   analysis. 
If  they  do  well,  they  are  excused  from  the  former  at  Christmas,  and  con- 
tinue with  analytical  chemistry;  otherwise  they  continue  the  course  in 
inorganic  chemistry  through  the   year.     A  few  students  from  selected 
schools  are  admitted  at  once  to  qualitative  analysis,  but  no  college  credit 
is  given. 

7.  Washington  and  Jefferson  University. — Students  from  a  few  selected 
schools  are  given  credit  for  the  first  year  of  chemistry  in  college,  provided 
they  take  a  later  course  in  chemistry  and  attain  a  high  pass  record.     Others 
are  required  to  pass  an  examination  before  any  credit  is  given.     Chemis- 
try is  given  in  the  sophomore  year  in  this  institution. 

8.  Wellesley  College. — An  advanced  course  is  provided  for  those  stu- 
dents who  have  had  a  year  of  chemistry.     Smith's  "College  Chemistry" 
is  used,  and  a  somewhat  exacting  line  of  experiments  is  required.     Some 
quantitative  experiments,  some  volumetric  analysis  and  some  inorganic 
preparations  are  included. 

9.  Chicago    University. — Students   who   have   completed   one   year   of 
chemistry  in  an  accredited  school  are  admitted  to  special  courses  and 
complete  the  work  preparatory  for  qualitative  analysis,  or    elementary 
organic  chemistry,  in  about  two-thirds  of  the  time  required  by  beginners; 
that  is,  they  complete  two  majors  in  chemistry  in  place  of  three.     The 
work  of  these  two  majors  is  carefully  adapted  to  utilize  and  clarify  the 
knowledge  already  gained. 

114 


10.  University  of  Michigan. — For  a  year  of  chemistry  at  an  accredited 
school  four  hours  of  university  credit  are  allowed   (sixteen  hours  per 
semester  is  full  credit).     These  students  are  admitted  to  a  course  some- 
what less  elementary  than  that  given  to  beginners. 

11.  University  of  Illinois. — A  full  year  of  chemistry  in  a  secondary 
school  is  accepted  in  place  of  one  semester  in  the  university,  provided  no 
more  chemistry  is  taken  (and  provided  chemistry  is  not  offered  for  en- 
trance).    When   the  student  continues  in  chemical  subjects  he  is  ad- 
vised to  take  the  regular  course  of  lectures  in  chemistry,  but  spends  less 
time  in  the  laboratory. 

12.  University  of  Wisconsin.-*- Credit  is  given  for  entrance  chemistry 
to  the  extent  of  one  or  two  units  out  of  fourteen.     These  students  enter 
the  same  classes  as  the  others,  but  have  a  slightly  different  laboratory 
course.     In  the  course  of  two  months  they  appear  to  be  on  about  the 
same  footing  as  those  taking  the  subject  anew. 

13.  Lehigh  University. — Up  to  two  years  ago  certain  certificates  were 
accepted  from  secondary  schools  but  the  results  were  so  unsatisfactory 
that  an  examination  has  been  substituted.     Those  who  fail  take  elementary 
chemistry;  those  who  pass  are  admitted  to  a  course  in  theoretical  chemis- 
try. 

14.  Sheffield  Scientific  School. — If  the  student  passes  entrance  chemis- 
try, he  is  allowed  to  take  an  examination  to  pass  off  the  elementary 
course  in  the  scientific  school,  and  if  successful  he  is  admitted  to  quali- 
tative analysis.     Very  few  students  are  thus  admitted. 

15.  Stevens  Institute   of   Technology. — Students   pass   an  entrance   ex- 
amination like  that  of  the  College  Entrance  Examination  Board,  but  the 
instructor  finds  that  he  cannot  make  use  of  the  earlier  work,  and  all  stu- 
dents take  a  course  in  elementary  chemistry. 

16.  Worcester  Polytechnic  Institute. — Earlier  attempts  to  examine  upon 
a  limited  portion  of  elementary  chemistry  with  the  purpose  of  definitely 
eliminating   this  from   the   college   course   were   not   successful.     Note- 
books are  now  examined,  and  when  these  indicate  a  satisfactory  course, 
the  students  are  placed  in  separate  divisions  and  given  a  different  labora- 
tory course.     They  attend  the  same  courses  of  lectures  as  the  beginners. 

17.  Massachusetts  Institute  of  Technology. — Students  who  have  satisfied 
the  entrance  elective  requirement  are  admitted  to  a  special  class  during 
the  first  term,  and  the  lecture  and  class-room  instruction,  as  well  as  the 
work  in  the  laboratory,  are  designed  to  take  advantage  of  the  work  al- 
ready completed  by  the  student  in  the  preparatory  school.     The  effort  is 
made  to  introduce  new  lines  of  experimentation,  as  well  as  to  reawaken 
interest  in  earlier  work  by  encouraging  the  student  to  interpret  the  phe- 
nomena which  he  now  studies  in  the  light  of  his  more  extended  expe- 
rience, and  with  the  aid  of  such  additional  concepts  as  have  been  introduced 
into  the  lectures  and  recitations.     The  two  divisions  of  the  class  are  uni- 
ted for  the  work  of  the  second  term. 

Of  these  seventeen  institutions  one  does  not  recognize  chemistry  for 
entrance,  two  make  no  specific  provision  for  students  who  have  had 
chemical  instruction  in  the  preparatory  schools,  three  provide  special 
laboratory  instruction,  but  give  no  definite  college  credit,  six  provide 
special  instruction  in  both  lecture  room  and  laboratory,  but  without 
giving  college  credit,  while  two  give  some  college  credit  on  certificate, 


and  four  excuse  students  from  elementary  college  courses  after  special 
examination. 

These  institutions  are  sufficiently  varied  as  to  locality  and  type  to 
justify  the  assertion  that  they  represent  the  present  practise  on  the  part 
of  thoughtful  college  teachers.  That  there  is  apparently  much  duplica- 
tion of  effort  is  at  once  evident,  and  that  this  must  result  in  some  loss  of 
time,  energy  and  enthusiasm  hardly  requires  argument.  Why,  then, 
have  we  so  long  tolerated  this  apparent  waste,  and  why  do  we  not  imme- 
diately take  steps  to  avoid  it?  The  answer  seems  to  me  to  be  this:  It 
appears  to  be  impossible  to  select  any  point  in  the  chemical  instruction 
received  by  the  members  of  a  college  entering  class  at  which  they  have 
such  a  sound  understanding  of  the  facts  and  principles  already  studied 
that  this  knowledge  may  safely  be  accepted  as  a  foundation  for  further 
college  instruction;  or,  if  such  a  point  may  be  selected,  it  lies  so  near  to 
the  beginning  of  the  college  course  as  to  make  a  definite  excuse  from  this 
small  amount  or  work  practically  meaningless.  There  is,  of  course,  a 
small  proportion  of  students  to  whom  this  statement  is  not  applicable, 
but  it  holds  true  to  so  large  a  proportion  that  it  determines  the  character 
of  the  instruction  which  is  given  to  all  students  who  have  had  any  pre- 
vious chemical  instruction.  The  situation  does  not  appear  to  be  appre- 
ciably better  in  institutions  having  a  definite  entrance  requirement  in 
chemistry  than  in  others. 

Some  of  the  reasons  for  this  state  of  affairs  we  will  try  to  consider 
presently,  but  let  us  first  look  at  the  conditions  as  they  confront  the  col- 
lege teacher  who  has  an  earnest  desire  to  enable  his  students  to  utilize 
every  advantage  which  they  have  gained,  remembering,  however,  that  in 
these  days  it  is  not  a  question  of  individual  but  of  class  instruction,  so 
far  as  the  main  features  of  a  course  are  concerned.  The  college  teacher 
or  the  teacher  in  a  technical  school  will  find  among  the  members  of  a 
single  class  students  of  each  of  the  following  types,  with  many  varia- 
tions : 

Student  A. — An  intelligent,  reasonably  thoughtful  pupil  from  a  school 
where  there  are  small  classes,  a  well-arranged  one-year  course  and  a 
judicious,  helpful  teacher.  Such  a  student  is  a  source  of  constant  pleas- 
ure, and  much  can  be  done  for  and  with  him. 

Student  B. — The  chemical  enthusiast  who,  during  a  course  of  one  or 
two  years'  duration  has  been  permitted,  because  of  his  enthusiasm,  to 
work  extra  hours  or  to  assist  his  teacher.  He  has  won  high  praise  and 
occasionally  merits  it,  but  too  often  the  college  teacher  learns  to  dread 
the  expenditure  of  energy  and  tact  which  is  necessary  to  retain  the  good 
will  of  such  a  student  while  bringing  him  to  realize  that  a  more  profound 
knowledge  than  his  own  may  be  possible;  yet,  when  the  battle  has  been 
won,  perhaps  half  of  these  men  make  excellent  students. 

Student  C. — The  student  who  has  had  two  years  of  chemistry,  in  a 
course  of  ordinary  excellence,  under  average  conditions  as  to  equipment 
and  teaching.  He  feels,  with  some  reason,  that  all  this  should  count 
for  a  great  deal,  and  no  argument  will  wholly  displace  this  notion.  He 
works  without  interest,  and  generally  badly,  and  is  a  heavy  load  to  carry. 
You  ask,  Why  not  transfer  him  to  the  work  of  the  higher  years?  We 
reply,  Because  experience  has  shown  that  he  probably  lacks  adequate 
preparation  for  it,  and  will  fail  in  it.  The  only  practicable  alternative 
lies  in  so  arranging  his  laboratory  practise  that  he  shall  have  as  large  a 

116 


measure  of  new  work  assigned  him  as  it  is  possible  to  oversee  without 
disproportionate  attention  on  the  part  of  the  instructors. 

Student  D. — A  student  of  moderate  ability  from  an  average  school 
with  a  year  of  experience.  His  credentials  are  clear,  but  he  has  perhaps 
had  little  personal  instruction  and  his  knowledge  is  ill-arranged  and 
vague,  as  to  both  fact  and  principle.  He  has  no  confidence  in  himself, 
and  there  is  very  little  which  is  final  in  his  preparatory  work.  His  is 
one  of  the  most  difficult  cases  to  provide  for  at  the  start,  but  often  turns 
out  well  in  the  end. 

Student  E. — A  student  who  has  spent  a  year,  or  more  rarely  two  years, 
under  inadequate  instruction,  which  has  been  worse  than  useless.  An 
entrance  examination  may  exclude  him,  but  under  other  systems  he  be- 
comes a  troublesome  factor  in  the  complex  problem  and  it  may  require 
some  weeks  to  discover  or  be  sure  of  his  trouble.  His  place  is  with  those 
students  who  take  up  the  study  of  chemistry  as  beginners  and  his  exclu- 
sion from  the  more  advanced  class  is  logical ;  but  a  transfer  to  elementary 
classes  when  these  are  provided  is  almost  certain  to  breed  discontent 
in  the  individual,  and  often  disarranges  other  work  of  the  term  which, 
by  that  time,  is  well  advanced. 

But  the  confusion  of  interest  does  not  end  here!  The  types  just  re- 
ferred to  have  been  selected  essentially  along  the  lines  of  general  efficiency 
of  instruction  and  length  of  courses.  It  must  further  be  recalled  that 
even  efficient  teachers  vary  widely  in  their  conceptions  of  the  ground  to 
be  covered,  and  the  college  receives  students  who,  during  a  single  year 
of  chemical  instruction,  have  had  the  chief  emphasis  laid  upon  descrip- 
tive chemistry;  others  where  it  has  been  laid  chiefly  on  "theoretical 
chemistry;"  again  others  where  the  course  is  largely  one  of  physics  rather 
than  chemistry;  and,  finally,  where  considerable  qualitative  analysis 
has  been  included  even  in  this  brief  time. 

The  conditions  appear,  then,  to  be  these,  briefly  stated:  Experience 
indicates  that  the  pupils  who  have  had  even  two  years  of  instruction  in 
secondary  schools  are,  in  general,  not  in  a  condition  to  take  up  work  in 
chemistry  which  is  more  advanced  than  that  of  the  first  year  in  the  col- 
lege, and  for  students  who  have  had  but  a  single  year  there  is  at  present 
so  little  that  can  be  regarded  as  common  knowledge  that  the  present 
apparent  duplication  of  work  seems  unavoidable.  Regarding  this  dupli- 
cation more  will  be  said  presently. 

Let  us  next  face  the  question,  Why  is  it  that  secondary-school  courses 
have  failed,  and,  as  it  seems  to  me,  are  likely  to  fail,  to  serve  as  substi- 
tutes for  any  considerable  amount  of  college  instruction  in  chemistry? 
The  reasons  are  far  from  simple,  and  they  need  some  analysis.  We  may 
distinguish,  I  think,  at  once  between  certain  factors  which,  since  they  are 
inherent  in  the  nature  of  our  science  or  in  the  period  in  the  pupil's  life 
in  which  the  instruction  is  given,  are  common  to  all  schools,  and  those 
elements  in  the  situation  which  are  the  outcome  of  varying  fitness  on  the 
part  of  the  instructors. 

Is  it  not  true  that  chemistry  itself  presents  some  peculiar  difficulties? 
It  is  often  said  that  "physics  is  taught  better  in  the  secondary  schools 
than  chemistry."  I  am  inclined  to  think  that,  as  a  general  statement, 
it  is  essentially  true.  But  might  not  the  full  truth  be  better  stated  in 
this  form:  "Physics  is  more  effectively  taught  than  chemistry  in  the 
secondary  schools  because  physics  is  an  easier  science  to  teach?"  It 

117 


is  true  that  chemical  phenomena  are  plentifully  at  hand,  and  that  our 
very  life  processes  are  dependent  upon  them;  yet  they  are  not  recognized 
as  such  and  are  essentially  unfamiliar.  The  teacher  of  chemical  science, 
and  the  practitioner  who  seeks  recognition  for  his  achievements,  are 
alike  forced  to  realize  that  the  tools  which  he  employs,  the  working  con- 
ditions which  he  establishes  and  the  terms  in  which  the  results  of  his 
labors  are  to  be  expressed  are  unusual  and  strange  and,  because  of  this, 
more  difficult  of  comprehension  by  his  fellow-men. 

The  beginner  in  chemistry  is  at  a  similar  disadvantage  as  compared 
with  the  beginner  in  physics.  In  his  work  in  physics  the  pupil  handles, 
for  example,  the  balance,  the  mirror,  the  pendulum  or  the  battery,  and 
he  makes  his  measurements  in  units  which  are  largely  familiar  to  him; 
and  the  phenomena  which  he  observes  are  not  foreign  to  his  daily  life. 
On  the  other  hand,  the  very  test-tube  and  beaker  to  which  the  student 
of  chemistry  is  immediately  introduced  are  unaccustomed  objects,  the 
bottle  of  acid  is  still  more  so,  and  we  often  accentuate  the  situation  by 
asking  him  to  don  breast-plate  and  armor  for  his  personal  protection, 
in  the  shape  of  aprons  or  rubber  sleeves.  While,  on  the  other  hand,  the 
concepts  and  laws  of  physics  may  not  be  properly  alluded  to  as  "easy," 
yet  it  seems  to  me  evident  that  they  make  less  demands  upon  the  intellect 
and  the  imagination  than  the  fundamental  principles  of  chemistry,  if 
these  principles  are  to  mean  more  to  the  pupil  than  mere  memorized 
statements. 

With  the  growth  of  the  holes  in  the  pupil's  clothing  the  strangeness  of 
the  beaker,  test-tube  and  acid  bottle  lessens,  to  be  sure,  but  he  is  coinci- 
dently  introduced  to  increasingly  complicated  phenomena;  he  is  asked  to 
conceive  of  molecules,  atoms,  ions,  even  of  electrons;  he  is  asked  to  form 
some  notion  of  valence,  to  construct  chemical  equations,  and  to  "state 
all  that  they  express" — a  thing  which  you  and  I  with  our  greater  wis- 
dom and  experience  may  well  hesitate  to  attempt.  He  must  master  the 
principles  of  stoichiometry,  that  branch  of  chemical  science  which  seems 
to  baffle  the  human  intellect  to  a  degree  that  never  ceases  to  amaze  even 
experienced  teachers.  It  may  even  happen  that  his  course  includes 
such  concepts  as  those  of  chemical  equilibrium,  the  mass  law,  or  the  phase 
rule  which,  in  their  relation  to  the  proper  subject  matter  of  a  secondary- 
school  course,  somehow  remind  one  of  the  records  of  those  early  chemical 
processes  found  in  the  first  chapter  of  Genesis  in  which  it  is  quite  inci- 
dentally stated  that  near  the  close  of  the  fourth  day  the  Lord  created 
"the  stars  also."  It  is  easier  to  forgive  the  ancient  recorder  for  his  lack 
of  a  due  sense  of  proportion  than  to  excuse  the  twentieth-century  instruc- 
tor. 

Keeping  in  mind,  then,  the  newness  of  the  chemical  processes  and  chem- 
ical concepts,  and  the  fact  that  the  latter  necessarily  make  considerable 
demands  upon  immature  imaginations,  may  we  not  fairly  ask  whether  it 
is  actually  reasonable  to  expect  that  a  young  boy  or  girl  of  fifteen  to  seven- 
teen will  gain  a  really  clear  insight  into  chemical  science  in  one  year; 
such  an  insight  as  will  serve  as  a  safe  foundation  for  a  chemical  super- 
structure without  further  strengthening  through  review?  I  think  I  can 
hear  teachers  answering  warmly  in  the  affirmative.  But,  again,  do  they 
not  have  in  mind  the  exceptional  rather  than  the  average  pupil?  It 
seems  to  me  that  experience  indicates  that  the  most  that  it  is  wise  to  at- 
tempt in  the  case  of  the  large  majority  of  pupils  of  the  ages  named  is  to 

118 


broaden  their  horizon  by  teaching  them  to  interpret  common  phenomena 
in  the  terms  of  chemistry,  and  with  the  aid  of  only  the  simplest  funda- 
mental principles  to  help  in  the  understanding  of  those  terms,  leaving 
the  meaning  of  the  more  abstract  conceptions  to  be  learned  in  a  college 
course,  or  by  later  and  more  mature  reading  if  the  pupil  is  not  destined 
for  college,  but  has  an  inquiring  mind.  I  believe  that  the  disparity  be- 
tween the  immaturity  of  mind  of  the  pupil  and  the  demands  of  the  sub- 
ject matter  assumed  to  be  taught  has  been  far  too  much  ignored.  I 
think  this  is  the  more  true  in  these  days  when  it  seems  evident  that  our  edu- 
cational system,  through  its  multiplicity  of  subjects  and  the  over-promi- 
nence of  the  baneful  influence  of  the  examination  paper,  tends  to  remove 
nearly  all  opportunity  for  concentrated  or  independent  thought  on  the 
part  of  the  pupil,  or  of  originality  in  methods  of  instruction  on  the  part 
ofthe  teacher. 

I  believe,  then,  that  even  the  competent  teacher,  with  adequate  equip- 
ment and  the  usual  time  allotment  must  find  great  difficulty  in  teaching 
chemistry  to  even  the  more  receptive  pupils  at  the  secondary-school  age 
so  thoroughly  as  to  permit  the  college  to  substitute  it  for  any  considerable 
part  of  the  college  course,  at  least  under  present  conditions.  For,  let  it 
be  said  with  all  humility,  we  college  teachers  too  often  made  a  sad  mess  of 
it  even  with  the  advantages  as  to  maturity  and  environment,  which  we 
presumably  possess. 

The  statement  is  sometimes  made  by  college  teachers  that  they  would 
prefer  to  receive  students  without  previous  chemical  experience,  and  the 
question  may  be  raised  whether  or  not  it  would  be  better  to  abandon 
entrance  requirements  in  chemistry.  I  believe  it  is  the  opinion  of  the 
majority  of  college  teachers,  especially  of  those  who  have  given  the  prob- 
lem the  most  careful  thought,  that  this  would  be  very  unfortunate.  I 
should  consider  it  so  far  at  least  two  important  reasons:  first,  because, 
while  formal  excuse  from  a  definite  portion  of  the  college  work  is  not  yet 
generally  practicable,  the  experience  already  acquired  by  the  student 
can  be  made  very  helpful  if  judiciously  utilized,  and  second,  because  it 
is  mainly  through  increased  cooperation  between  the  schools  and  the 
colleges  in  an  effort  to  secure  better  working  conditions  for  the  teacher, 
and  the  adoption  of  a  rational  course  of  instruction  in  the  secondary 
schools,  which  will  take  into  account  all  of  the  pupils,  rather  than  those 
alone  who  propose  to  enter  college,  that  we  may  hope  to  attain  better 
results. 

It  is  noticeable  in  the  statements  quoted  above  regarding  the  present 
practise  in  the  various  institutions,  that  the  state  colleges  are  apparently 
giving  a  greater  amount  of  definite  credit  for  work  in  the  secondary 
school  than  the  others.  This  is  frankly  stated  by  some  of  the  college 
teachers  to  be  due  to  the  closer  organic  connection  of  the  state  university 
with  the  general  school  system,  and  is  admittedly  done  under  slight 
pressure.  On  the  other  hand,  these  institutions  have,  through  the  system 
of  school  inspection  on  the  part  of  the  state  universities,  a  more  direct 
means  of  influencing  instruction  in  the  preparatory  schools.  The  outlook 
for  better  conditions  in  the  future  is  generally  regarded  as  favorable. 

Perhaps  we  may  ask  just  here,  What  would  these  better  conditions  be 
like?  It  is  probably  fair  to  say  that  they  would  be  such  as  to  avoid 
duplication  of  work.  Obviously  repetition  and  duplication  should  be 
reduced  to  a  minimum,  and  no  one  would  welcome  changes  which  tend 

119 


8 

to  bring  this  about  more  than  I.  But  I  think  it  is  possibly  true  that 
there  is  less  actual  duplication  of  work  than  is  commonly  supposed  in 
those  institutions  in  which  the  students  who  have  had  a  year  or  more  of 
chemical  instruction  are  segregated  in  separate  divisions.  Let  us  take 
a  concrete  case  by  way  of  illustration.  The  pupil  in  the  secondary  school 
prepares  chlorine,  using  salt,  sulphuric  acid  and  manganese  dioxide,  or 
hydrochloric  acid  and  manganese  dioxide.  The  time  available  rarely 
permits  the  use  of  any  other  method,  and  the  chemical  changes  involved 
are  sufficiently  complex  to  present  some  little  difficulty  for  their  complete 
comprehension.  Few  pupils,  as  experience  shows,  really  understand 
that  this  is  a  typical,  and  not  an  isolated  or  unique  procedure,  and  the 
rdle  played  by  the  manganese  dioxide  is  but  vaguely  grasped.  It  is 
true  that  such  students  are  asked  to  again  prepare  chlorine  from  these 
materials  in  the  college  laboratory,  but  they  are  at  the  same  time  required 
to  study  the  action  upon  hydrochloric  acid  of  such  agents  as  lead  dioxide, 
barium  dioxide,  hydrogen  dioxide,  potassium  permanganate  or  potassium 
dichromate,  and  to  discuss  the  changes  involved  from  the  common  point 
of  view  of  the  oxidation  of  the  acid,  and  the  proportion  of  actual  duplica- 
tion of  work  is  really  small.  Similarly,  in  the  study  of  the  action  of  acids 
upon  metals,  while  it  is  desirable  to  ask  the  student  for  the  sake  of  com- 
pleteness to  repeat  the  familiar  process  for  the  preparation  of  hydrogen 
from  zinc  and  sulphuric  acid,  this  becomes  a  mere  incident  in  the  series 
of  experiments  and  in  the  broader  discussion  of  all  phenomena  observed 
which  may  well  go  so  far  as  to  include  the  principles  of  solution  tension, 
in  the  case  of  such  students. 

It  is,  apparently,  work  of  this  general  character  which  many  college 
teachers  are  offering  to  those  who  have  had  earlier  chemical  training. 
The  laboratory  work  is,  as  we  have  seen,  frequently  accompanied  by 
lecture  demonstration  and  recitations  of  a  corresponding  grade,  and  while 
it  does  not,  of  course,  appeal  to  the  student  as  a  step  in  advance,  as  would 
some  other  procedure  which  seemed  to  give  a  stamp  of  finality  to  his 
earlier  studies,  it  may  well  be  questioned  whether  it  does  not  better  foster 
his  intellectual  welfare  than  the  more  alluring  plan  could  do.  It  should, 
however,  be  the  purpose  of  the  college  teacher  to  keep  closely  in  touch 
with  the  actual  and  probably  increasing  average  attainments  of  the  pupils 
sent  to  him,  in  order  that  he  may  take  all  proper  advantage  of  the  instruc- 
tion already  given,  and  it  is  probably  true  that  a  larger  number  of  insti- 
tutions should  offer  such  moderately  advanced  courses  than  is  at  present 
the  case. 

I  propose  next  to  refer  briefly  to  one  or  two  specific  points  at  which  it 
appears  to  me  that  the  instruction  in  the  secondary  schools  might  be 
improved.  I  do  this  with  much  hesitation,  for  I  realize  that  those  very 
details  or  methods  which  perhaps  fail  to  appeal  to  me  may  well  be  very 
dear  to  another,  and  I  realize  that  I  should  be  loath  indeed  to  have  the 
actual  efficiency  of  my  own  instruction  judged  by  certain  alleged  quota- 
tions on  the  part  of  some  of  my  students,  or  even  by  the  subsequent  acts 
of  many  of  them.  A  conspicuous  instance  of  the  failure  of  some  of  our 
hopes  was  afforded  by  a  statement  made  by  one  of  our  students  in  a  recent 
written  test  that  "nitroglycerine  is  used  as  a  lubricant." 

A  question  which  many  find  difficult  to  answer  is  this:  How  far, 
taking  into  account  existing  and  not  idealized  conditions,  is  it  just  to  re- 
gard note-books  as  an  index  of  the  efficiency  of  the  instruction  as  given 

120 


in  a  particular  school,  or  college?  I  shall  not  be  rash  enough  to  under- 
take to  answer  this  beyond  expressing  a  conviction  that  while  a  note- 
book which  is  well  kept  and  carefully  corrected  probably  indicates  care- 
ful, efficient  teaching,  a  relatively  poor  note-book  may  represent  more 
accurately  an  overburdened  condition  of  the  teacher,  which  prevents 
adequate  inspection  and  correction,  than  actual  inefficiency  in  instruc- 
tion. For  it  is  often  true  that  much  of  apparent  error  in  the  records 
may  have  been  actually  corrected  in  conference  or  class-room.  This 
does  not,  however,  apply  to  some  of  the  atrociously  bad  specimens 
which  are  occasionally  met  with,  nor,  on  the  other  hand,  does  it  ignore 
those  note-books  which  are  obviously  not  records  of  work  done,  but  stud- 
iedly prepared  exhibits,  executed  through  connivance  of  teacher  and 
pupil  at  the  expense  of  a  fundamental  principle  of  all  scientific  work, 
rigid  honesty. 

Is  it  not  true  that  too  many  teachers  are  contented  to  have  their  stu- 
dents perform  more  or  less  perfunctorily  the  magic  "forty  experiments" 
which  are  said  by  some  one  else  to  represent  a  suitable  course,  rather  than 
to  vitalize  their  instruction  by  devising  ten,  twenty-five,  fifty-five  or 
any  other  number  of  experiments  of  their  own  to  illustrate  the  facts  or 
principles  which  they  themselves  desire  to  fix  in  the  pupils'  minds,  and 
to  see  that  these  are  actually  discerned.  The  busy,  often  overburdened 
teacher,  will  not  always  find  time  or  energy  to  devise  an  entire  course 
of  instruction,  but  the  introduction  of  even  a  limited  amount  of  well- 
considered  experiments  or  class-room  instruction  which  represents  the 
personal  equation  of  the  individual  teacher  does  much  to  maintain  en- 
thusiasm for  the  teaching  which  is  often  reflected  in  the  work  of  the  pupils 
as  well. 

The  deadening  tendency  of  a  mere  following  of  a  course  of  experiments 
laid  down  by  others  shows  itself  also  in  a  disposition  to  regard  each  ex- 
periment as  a  thing  apart,  the  nominal  completion  of  which  is  a  cause 
mainly  for  relief,  is  also  reflected  in  many  instances  in  the  notes  sub- 
mitted, which  are  long  and  minutely  descriptive  of  really  insignificant 
details,  but  miss  the  real  point  of  the  experiment.  This,  in  turn,  comes 
from  the  fact  that  the  pupil  is  not  sufficiently  informed  why  he  is  asked 
to  perform  the  experiment  at  all,  and  in  the  strangeness  of  the  work  he 
naturally  confuses  the  important  and  the  unimportant.  For  example, 
he  is  often  apparently  left  to  think  that  a  description  of  "the  apparatus 
used"  is  as  essential  when  he  pours  silver  nitrate  solution  from  a  bottle 
into  a  test-tube  containing  a  halide  solution,  as  when  he  is  preparing 
nitric  acid  from  saltpeter,  and  he  elaborates  his  descriptions  with  the  same 
fidelity  in  the  former  ease  as  in  the  latter,  with  a  very  considerable  aggregate 
loss  of  good  energy  on  his  part  and  that  of  his  instructor.  But  that  is 
not  the  worst  of  it,  for  he  gains  an  idea  that  all  experiments  are  to  be 
treated  with  similar  uniformity  in  other  respects,  even  including  his 
search  for  their  hidden  meanings.  I  do  not,  of  course,  advocate  telling 
the  student  what  is  to  happen  and  then  asking  him  to  say  that  it  did  oc- 
cur, adding,  possibly,  the  color  of  a  precipitate;  but  I  do  believe  that  a 
great  deal  would  be  gained  if  nearly  all  experiments,  or  groups  of  experi- 
ments, were  more  carefully  prefaced  in  the  laboratory  directions  by  a 
brief  statement  regarding  the  principles  or  the  types  of  changes  involved, 
and  if,  then,  the  student  were  encouraged  to  make  his  observations  with 
reference  to  these  statements  and  were  required  to  show  that  he  under- 

121 


IO 

stands  how  the  given  experiment  actually  confirms  the  points  in  ques- 
tion. This  would  do  much  to  avoid  what  is  at  present  a  wasteful  expendi- 
ture of  time,  muscular  energy  and  eyesight — all  of  which  could  be  used 
to  increase  the  pupil's  experience,  and  it  would  partially,  at  least,  elim- 
inate the  vague  groping  which  results  as  those  appalling  scientific  mon- 
strosities which  follow  the  words  "I  conclude"  in  the  note-book  of  many 
a  conscientious  student.  Have  you  ever  recalled  the  bewilderment  of 
your  student  days,  when  you  had  no  idea  what  to  look  at  among  so  many 
phenomena?  Have  you  ever  taken  a  half  dozen  experiments  and  can- 
didly asked  yourself  what  you  can  legitimately  conclude  from  what  has 
been  performed?  It  is  very  much  like  trying  to  answer  some  of  one's 
own  well-sounding  examination  questions:  a  procedure  which  often  causes 
them  to  lose  their  attractiveness. 

Do  we  not  then,  tend  to  lay  too  much  stress  upon  mere  performance 
of  experiments,  and  devote  too  much  time  to  the  making  and  reading 
of  descriptive  notes  which  are  often  copies  of  the  experiment  manual, 
and  too  little  time  to  helping  the  pupil,  through  judicious  suggestions 
regarding  the  experiments  and  through  questioning  at  the  work-table 
and  in  the  recitation  room,  to  comprehend  what  it  is  all  about,  and  the 
relation  of  a  given  experiment  to  others  already  performed? 

In  order  that  the  perplexities  of  the  college  instructor  may  be  brought 
more  clearly  to  mind,  and  in  order  to  illustrate  certain  types  of  note- 
books, I  reproduce  here  a  few  pages  from  the  books  presented  in  connec- 
tion with  the  entrance  elective  requirement  of  the  Massachusetts  Insti- 
tute of  Technology.  The  first  (Fig.  i)  is  a  representative  of  a  rather  small 
number  of  superior  books.  The  observations  are  carefully  recorded,  the 
deductions  are  valid  and  well  expressed  and  there  is  evidence  (not  shown 
in  the  cut)  that  the  note-book  had  been  inspected  and  corrected.  Un- 
der existing  conditions  as  to  numbers  of  pupils  to  be  taught  it  is  probably 
too  much  to  expect  that  all  will  attain  a  standard  which  this  note-book 
appears  to  represent.  To  all  appearances  the  records  are  original  and 
the  instruction  efficient. 

The  pages  reproduced  in  Figs.  2  and  3  are  of  a  not  uncommon  type. 
The  first  leaves  one  in  doubt  as  to  what  part  of  the  work  has  been  per- 
formed by  the  pupil,  since  the  statements  made  regarding  the  physical 
properties  could  have  been  copied  from  a  book,  the  records  of  experi- 
ments performed  are  distinctly  wrong  and,  in  the  case  of  the  alleged 
preparation  of  chlorine,  would,  if  ever  followed,  lead  more  directly  to  a 
residence  at  a  hospital  than  to  any  worthy  scientific  end.  Fig.  3  shows 
a  page  which  makes  no  pretense  of  being  anything  more  than  a  mere 
record  of  a  useless  mixing  of  a  few  solutions,  and  moreover  these  records 
are  also  entirely  wrong. 

The  two  pages  just  commented  upon  did  not  bear  any  evidence  of  in- 
spection on  the  part  of  the  teacher ;  that  shown  in  Fig.  4  bore  the  stamped 
legend  "approved,"  but  a  careful  inspection  leaves  one  in  doubt  as  to 
what  particular  feature  of  the  record  warranted  this,  unless  it  may  be 
the  evidence  of  sympathy  (?)  on  the  part  of  the  pupil  with  the  tendency 
towards  spelling  reform. 

These  are  not  exceptional  pages;  they  are  representatives  of  many 
that  pass  under  our  inspection  each  year,  and  I  ask  you,  with  all  sym- 
pathy for  the  teachers  concerned,  what  evidence  does  any  but  the  first 
give  that  one  may  safely  omit  a  review  of  the  ground  supposed  to  be 

122 


Fig.  1. 


Fig.  2. 


Fig.  3. 


Fig.  4. 


II 

covered  by  this  work  in  a  college  course  which  is  primarily  expected  to 
furnish  a  safe  foundation  on  which  there  is  afterwards  to  be  erected  a 
very  considerable  superstructure  of  chemical  knowledge?  Are  we  not 
justified  in  our  perplexities? 

I  should  like  also  to  appeal  to  the  teachers  in  the  preparatory  schools 
to  encourage  the  pupils  to  better  economize  their  laboratory  time.  Too 
many  are  allowed  to  placidly  watch  a  crucible  heat,  or  a  solution  boil, 
when  other  experiments  might  be  in  progress  at  the  same  time,  and  these 
habits  are  difficult  to  overcome.  I  should  like  to  suggest,  too,  that  some 
of  the  most  promising  pupils  are  often  seriously  harmed  by  allowing  them 
to  work  too  much  by  themselves,  or  by  encouraging  them  to  go  beyond 
their  depth  in  a  particular  line  in  which  they  appear  to  be  specially  in- 
terested, to  the  detriment  of  their  fundamental  work.  Some  pupils 
usually  come  to  college  with  an  exaggerated  sense  of  their  own  attain- 
ments and  it  frequently  requires  long  and  tactful  persuasion  on  the  part 
of  the  college  instructor  before  they  can  be  reduced  to  reasonable  humility. 

On  the  other  hand,  I  venture  to  plead  that  all  proper  encouragement 
be  given  to  pupils  to  take  advantage  of  such  special  privileges  as  the  col- 
leges offer.  It  is  not  an  infrequent  occurrence  to  find  a  pupil  who  tells 
us  that  he  has  been  advised  by  his  teacher  to  take  the  elementary  course 
for  beginners  as  one  in  which  he  will  incur  less  risk  of  failure.  Were 
the  examination  the  goal  of  the  course,  there  obviously  would  be  little 
to  criticize  in  this  suggestion;  its  effect  upon  the  student  as  an  embryo 
scientist  is  seldom  happy. 

In  conclusion  let  us  ask,  how  can  we  make  the  work  in  chemistry  in 
the  various  institutions  more  mutually  helpful? 

1.  By  a  more  extensive  cooperation  on  the  part  of  the  colleges  and 
technical  schools  in  the  way  of  separate  courses  for  those  who  have  taken 
chemistry  before  entrance,  a  closer  study  of  the  problem  on  the  part  of 
all,  and  a  readiness  to  recognize  improved  conditions. 

2.  By  an  intelligent  delimitation  of  the  secondary-school  course,  so 
that  it  will  only  offer  what  the  pupil  can  best  assimilate  at  the  age  and  in 
the  environment  in  which  he  works.     This  is  too  large  a  topic  for  dis- 
cussion in  this  connection,  and  it  is  sadly  complicated  by  the  necessity 
for  furnishing  a  course  which  shall  be  alike  useful  for  the  pupil  who  ex- 
pects to  enjoy  college  opportunities  and  his  less  fortunate  associate.     I 
plead,  as  I  have  often  done,  for  a  course  which  is  fundamentally  descrip- 
tive in  its  character.     I  do  not  mean  a  mere  catalogue  of  facts,  but  a  course 
in  which  selected  facts  are  taught  for  some  specific  reason,  which  is  in- 
variably explained  to  the  pupil,  and  in  which  these  facts  are  interpreted 
for  him  in  terms  of  the  simplest  of  the  fundamental  principles  and  con- 
cepts, so  often  repeated  and  constantly  utilized  that  they  may  ultimately 
mean  more  than  memorized  paragraphs  from  what  he  may  later  remem- 
ber only  as  "a  book  with  a  green  cover."     I  think  there  can  be  no  greater 
mistake  than  to  suppose  that  such  a  course  is  a  less  worthy  one  than  such 
as  is  often  pointed  to  with  pride  as  a  "theoretical  course,"  and  no  teacher 
should  consider  that  it  will  demand  less  than  his  best  efforts,  supplemented 
by  all  his  knowledge,  to  utilize  the  opportunities  for  helpful  and  thorough 
instruction  which  such  a  course  affords.     It  is,  of  course,  difficult  to  de- 
termine whether  or  by  how  much  the  instruction  of  the  boy  or  girl  destined 
for  college  should  be  differentiated  from  that  of  their  fellow-students, 
but  I  venture  to  hope  that  a  decision  may  yet  be  reached,  through  coflpera- 

123 


12 


tion,  which  may  permit  us  to  select  a  limited  field  which  shall  be  so  well 
covered  as  not  to  necessitate  repetition  in  college,  and  that  this  may  be 
done  without  prejudice  to  the  candidate  or  non-candidate  for  college 
credits.  How  soon  this  will  come,  or  how  large  this  field  may  be,  I  do 
not  venture  to  predict. 

3.  By  increasing  the  time  allotted  to  chemistry  in  the  secondary  schools 
until  it  is  more  nearly  commensurate  with  the  dignity  and  difficulty  of 
the  subject.  Whether  such  increase  should  amount  to  one  third,  or 
some  larger  fraction  of  the  present  time  allotment  is  a  point  which  those 
actively  concerned  in  the  teaching  can  best  determine.  The  increase  in 
time  should  be  asked  for  mainly  in  the  interests  of  those  who  will  not  pur- 
sue the  study  of  chemistry  further,  but  it  will  also  presumably  hasten 
the  time  when  a  definite  point  of  articulation  with  the  college  work,  as 
just  suggested,  can  be  fixed. 

Finally,  there  is  the  urgent  need  of  decreasing  the  demands  made  upon 
the  teacher  of  chemistry  in  the  secondary  school  for  duties  other  than 
those  of  chemical  instruction,  and  also  a  critical  need  for  relatively  more 
instructors.  I  believe  that  a  very  large  proportion  of  the  unsatisfactory 
results  now  noticeable  are  due  to  the  fact  that  in  most  of  our  schools  it  is 
not  humanly  possible  for  the  teaching  force  to  accomplish  what  should  be 
expected  of  them,  or  to  be  at  the  desk  of  the  pupil  when  he  reasonably 
needs  assistance.  In  some  schools  which  have  come  under  my  observa- 
tion the  distribution  of  supplies  must  be  attended  to  by  the  senior  (or 
often  the  only)  instructor,  an  operation  which  consumes  a  half  hour  or 
more. 

Probably  no  science  demands  for  its  understanding  by  the  beginner 
more  individual  instruction  in  laboratory  and  class-room  than  chemistry, 
and  the  school  authorities  should  realize  this.  When  they  do  we  shall 
have  much  cause  for  rejoicing,  and  much  of  the  present  groping  and  be- 
wilderment on  the  part  of  the  young  student  will  give  place  to  enjoyment 
in  the  study  of  a  science  which  is  really  second  to  none  in  its  attractive- 
ness or  value  when  pursued  under  favorable  conditions. 

It  is  a  pleasure,  in  closing,  to  say  that  I  feel  that  too  much  praise  can 
hardly  be  given  to  the  loyal,  hard-working,  intelligent  and  inspiring 
teachers  who  are  accomplishing  so  much  in  behalf  of  our  science  in  the 
training  of  the  beginners.  No  thoughtful  college  teacher  can  fail  to 
recognize  the  good  work  done  in  very  many  schools  throughout  the  coun- 
try, and  while  many  feel  that  more  definite  recognition  in  the  college 
curriculum  can  not  wisely  be  given  to  this  work  at  the  present  time,  I 
am  sure  from  the  messages  which  have  recently  come  to  me  from  many 
colleagues  in  many  institutions  that  there  is  an  increasing  appreciation 
of  the  fact  that  the  way  to  better  things  lies  through  a  sympathetic  ap- 
preciation and  study  of  our  common  problem  and  our  common  difficul- 
ties. 1 

1  In  a  discussion  which  followed  the  presentation  of  this  and  other  papers  on 
educational  topics,  a  statement  was  made  by  a  secondary  school  teacher  of  recognized 
standing  to  the  effect  that  many  such  teachers  had  become  indifferent  to  the  opinions 
of  college  instructors,  since  it  is  "impossible  to  satisfy  them  any  way."  While  I 
heartily  sympathize  with  the  thoughtful  teacher  who  desires  to  teach  his  subject  in 
his  own  way  and  with  his  own  ideals  in  view,  and  deplore  any  attitude  of  the  colleges, 
collectively  or  individually,  which  tends  to  interfere  with  this,  it  seems  to  me  that  the 
common  cause  of  greater  total  efficiency  in  instruction  can  hardly  be  served  by  ignoring 

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i 

If  there  can  be  a  determination,  on  the  one  hand,  to  undertake  only 
so  much  as  can  be  well  taught  and  to  give  the  largest  practicable  vitality 
to  the  instruction,  and,  on  the  other  hand,  a  disposition  to  promptly 
recognize  and  utilize  every  bit  of  ground  gained  which  offers  a  secure 
foundation  for  later  work,  a  more  satisfactory  situation  than  that  which 
exists  at  present  can  hardly  fail  to  result,  even  though  the  degree  of 
recognition  of  secondary  school  instruction  may  fall  short  of  that  which 
some  desire.  H.  P.  TALBOT. 

MASSACHUSETTS  INSTITUTE 
OF  TECHNOLOGY. 


HIGH  SCHOOL  CHEMISTRY:  THE  CONTENT  OF  THE  COURSE.1 

Every  teacher  in  the  high  school  of  to-day  finds  himself  in  stimulating 
circumstances.  He  is  obliged  to  question  himself  closely  as  to  the  part 
that  his  subject  plays  in  the  curriculum,  for,  at  least  in  the  large  cities, 
the  long-discussed  change  in  the  character  of  the  high  school  is  upon  us. 
The  reason  for  the  change  is  found  in  a  realization  of  the  facts  that  in  the 
past,  high  school  education  has  been  enormously  wasteful;  that  eighty 
to  ninety  per  cent,  of  our  pupils  do  not  complete  the  course;  that  only  a 
small  part  of  the  remaining  per  cent,  achieve  the  purpose  for 
which  the  whole  course  has  been  framed,  that  of  entering  college. 
The  evidence  that  the  change  has  actually  begun  is  found  in  the  estab- 
lishment of  trade  and  vocational  schools,  in  the  frequent  discussion  of 
questions  pertinent  to  these  points,  and  in  the  statements  of  principals 
and  superintendents  that  something  must  be  done  to  stop  the  enormous 
educational  waste;  and  in  their  declaration  that  the  high  school  must 
meet  real  needs,  must  give  the  boy  or  girl  the  education  that  is  best  for 
him  or  her,  as  a  member  of  the  human  group,  with  little  reference  to  col- 
lege entrance. 

Among  the  changes  that  are  coming  from  a  recognition  of  these  facts, 
we  find  the  importance  of  science  in  the  high  school  largely  increased. 
The  fact  that  it  is  science  that  has  produced  the  great  material  advance 
of  the  past  century  makes  it  certain  that  in  the  further  turning  from  formal 
to  practical  education,  science  will  play  a  larger  part.  It  is  the  purpose 
of  this  paper  to  inquire  into  the  manner  in  which  these  changing  condi- 
tions are  reacting  on  the  high  school  course  in  chemistry,  and  to  discuss 
some  of  the  considerations  that  are  determining,  or  should  determine, 
a  new  course  of  study.  The  speaker  wishes  also  to  discuss,  in  general, 
the  problem  of  high  school  chemistry,  presenting  personal  and  perhaps 
even  extreme  points  of  view. 

We  may  classify  the  various  forces  that  are  shaping  the  new  course  as 
external  and  internal.  In  the  first  class  we  find:  (a)  a  lessening  of  the 
college  influence,  due  to  a  realization  of  the  necessity  of  educating  for 
other  purposes  than  college  entrance;  (6)  a  tendency  to  put  chemistry 

the  opinions  of  the  colleges,  even  if  they  are  mistaken.  May  it  not  be  true  that  the 
secondary  school  teachers  lack  some  courage,  or  at  least  some  persistence,  in  forcing 
their  convictions  upon  the  college  teacher?  They  have  the  privilege  of  speaking  from 
a  fullness  of  experience  with  the  young  pupil  which  the  college  instructor  usually  lacks. 
1  Presented  at  the  second  decennial  celebration  of  Clark  University,  Worcester, 
Mass.,  September  16,  1909. 

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14 

earlier  in  the  course  and  to  give  a  second  year  of  it;  (c)  what  we  may  call 
the  lay  demand  for  practical  education. 

The  lessened  college  influence  will  give  to  the  body  of  secondary  teach- 
ers not  only  greater  freedom  in  the  selection  and  arrangement  of  their 
material,  but  what  is  of  even  more  importance,  because  it  serves  as  a 
stimulus  to  their  creative  ability,  a  realization  of  the  importance  of  their 
own  great  work  and  their  responsibility  for  it.  The  lack  of  this  kind  of 
freedom  is  in  part  responsible  for  the  condition  that  exists  to-day  when 
the  high  school,  paying  comparatively  high  salaries,  can  not  get  enough 
good  men,  while  the  college  apparently  has  more  than  it  needs  at  a  smaller 
compensation.  This  is  not  the  least  of  the  evils  that  have  resulted  from 
the  college  domination  of  the  high  school.  Others  have  often  been 
pointed  out  and  are  well  known.  The  course  of  study  can  never  be  adapted 
to  the  real  needs  of  the  high  school  so  long  as  it  is  framed  by  the  college, 
at  the  best  a  force  operating  at  a  distance,  at  the  worst  a  power  acting 
for  needs  it  cannot  know.  The  college,  as  far  as  the  high  school  was  con- 
cerned, always  had  the  idea  of  preparation,  not  growth,  in  mind.  A 
thousand  boys  went  through  a  course  in  chemistry  whose  nature  was 
determined  solely  by  the  needs  of  the  three  or  four  who  were  to  be  trained 
to  be  expert  chemists.  It  is  often  said  at  this  point  that  the  course  which 
best  prepares  the  pupil  for  advanced  work  is  also  best  for  every  other 
boy.  It  is  nearer  the  truth  to  say  that  the  education  which  best  meets 
the  needs  of  the  growing  member  of  the  human  whole  ought  to  be  the 
best  preparation  for  college. 

Chemistry  earlier  in  the  course  and  perhaps  a  second  year  of  it;  the  first 
of  these  conditions  may  bring  dismay  to  many  teachers;  the  second, 
delight  to  all,  surely.  Certainly  some  changes  in  the  traditional  course 
are  necessary  in  teaching  chemistry  in  the  second  year.  On  this  point 
the  speaker  can  refer  to  an  experience  covering  nearly  seven  years.  During 
all  that  time  chemistry  has  been  taught  to  some  second-year  students. 
At  times  fourth-year  students  and  second-year  students  have  been  taking 
nearly  the  same  course  simultaneously  in  separate  classes;  at  other  times 
the  two  terms  of  students  have  been  mixed  in  the  same  class.  In  both 
cases  a  certain  degree  of  success  with  the  second-year  students  has  been 
obtained,  even  if  we  judge  by  no  other  standards  than  results  of  college 
entrance  and  state  board  examinations.  Speaking  for  the  moment  from 
the  standpoint  of  the  college  entrance  syllabus,  but  little  change  is  neces- 
sary to  adapt  the  chemistry  to  second-year  students.  A  less  rigorous 
insistence  on  the  philosophical  development  of  the  atomic  and  other 
hypothesis  seems  to  be  the  most  necessary  item  of  change.  In  any  case, 
as  far  as  the  ability  of  the  student  to  comprehend  is  concerned,  the  differ- 
ence between  individuals  is  much  greater  than  the  difference  between 
second-  and  fourth-year  classes.  The  general  average  of  work  is  consid- 
erably better  in  fourth-year  classes,  but  this  is  explained  largely  by  the 
dropping  out  of  weak  material. 

To  meet  the  demand  for  practical  education,  we  find  that  there  is  a 
decided  tendency  to  introduce  into  the  high  school  a  great  deal  more  of 
chemical  technology  than  there  was  in  the  older  course.  There  are  some 
who  go  so  far  as  to  say  that  the  high  school  ought  to  give  the  pupil  a  means 
of  earning  his  living;  that  chemistry  should  be  taught  so  as  to  fit  him  for 
some  direct  employment  in  practical  occupations.  While  admitting 
this  as  a  possible  ideal,  the  view  implies  such  an  extreme  change  in  the 

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character  of  the  high  school  that  it  is  not  advisable  to  take  it  into  con- 
sideration in  the  present  discussion,  except  to  admit  that,  given  time,  it 
would  be  possible  to  accomplish  this  result.  Along  with  the  demand 
for  technical  education,  we  find  a  tendency  to  fill  the  course  with  a  great 
deal  of  matter  that  is  associated  with  the  home  and  every-day  life.  These 
two  demands  have  come  largely  from  without.  They  have  done  great 
good  and  have  added  much  to  the  human  interest  of  our  science.  We 
teachers  are  very  prone  to  an  academic  point  of  view,  and  the  stimulus 
has  been  a  needed  one.  Yet  with  the  good,  there  is  some  danger.  There 
is  a  tendency  in  some  quarters  to  emphasize  the  technological  details 
of  processes,  to  fill  the  discussion  with  technical  terms,  so  that  the  pupils' 
talk  bristles  with  tuyeres  and  downcomers  and  the  particular  names  of 
the  many  towers  that  find  application  in  manufacturing  chemistry. 
The  chief  evil  of  this  kind  of  instruction  is  that  it  produces  rather  showy 
results,  it  seems  to  indicate  more  knowledge  than  really  exists.  More- 
over, a  technical  process  of  to-day  is  a  very  complicated  thing.  It  is 
improved  every  year  and  we  find  to  our  discomfiture,  on  visiting  the 
factory,  that  the  process  we  have  so  carefully  learned  from  the  text- 
book differs  in  a  hundred  details  from  that  actually  employed. 

The  chemical  interpretation  of  the  ordinary  phenomena  of  the  house- 
hold is  a  very  interesting  matter.  Unfortunately  many  of  these  inter- 
pretations are  very  complex,  others  are  unknown.  Some  are  simple 
enough  to  be  comprehended  by  a  beginner,  and  certain  food  tests  and 
the  like  can  be  taught  so  that  the  pupil  can  go  through  them  in  a  more 
or  less  mechanical  fashion.  But  surely  these  do  not  constitute  a  suita- 
ble vehicle  for  the  transmission  of  that  highly  organized  mass  of  knowl- 
edge and  way  of  thinking  which  we  know  as  chemistry.  The  intellec- 
tual and  material  advance  that  our  science  has  brought  to  the  world  has 
not  come  from  the  knowledge  of  isolated  test-tube  reactions,  but  from 
the  brilliant  imaginings  of  the  authors  of  its  great  hypotheses,  from  the 
realizations  of  its  tremendous  generalizations,  from  the  perceptions  of 
most  deeply  hidden  relationships  among  the  things  that  we  call  matter. 
If  this  that  we  teach  our  pupils  is  to  bear  the  name  of  chemistry,  it  must 
give  them  at  least  a  glimpse  of  these  deeper  things.  Technological  chem- 
istry and  household  chemistry  have  a  very  proper  place  in  the  high  school 
course,  but  they  should  never  be  over-emphasized.  They  afford  the 
illustrative  material  which  the  good  teacher  will  constantly  use  to  give 
interest  to  his  work  by  showing  what  good  the  science  has  brought  to 
mankind.  But  a  course  composed  almost  wholly  of  such  material,  as 
has  been  proposed,  would  not  be  chemistry,  and  it  would  probably  not 
be  science.  There  would  be  an  absence  of  principles  of  relationships. 
A  pupil  might  indeed  learn  that  there  exists  a  simple  process  for  the 
manufacture  of  soda,  but  he  would  not  share  in  any  degree  the  kind  of 
thinking  that  has  made  this  and  a  thousand  other  processes  possible. 
I  hold  that  it  is  our  chief  duty  to  give  him  this  kind  of  knowledge. 

Coming  then  to  the  internal  considerations  which  shall  help  shape  our 
new  course  of  study,  we  must  inquire  what  high  school  chemistry  should 
seek  to  accomplish  for  the  pupil.  One  way  of  answering  this  question  is 
by  asking  ourselves  what  it  has  done  for  us  as  individuals.  We  know 
that  it  has  made  us  broader  men  and  freer  human  beings,  and  it  is  fitting 
that  we  should  seek  to  have  our  pupils  attain  in  some  degree  this  high 
end.  Again,  it  is  certain  that  one  who  has  been  through  a  good  course 

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in  chemistry,  who  has  learned  the  principles  of  chemical  action,  and  com- 
prehended the  great  laws  that  the  science  has  revealed,  looks  upon  the 
world  about  him  in  an  altogether  new  way,  so  much  so  that  with  the 
increase  in  the  general  knowledge  of  science  there  is  being  produced  a 
new  type  of  world  mind.  Our  pupils  must  be  taught  so  that  they  shall 
share  in  this  new  world  mind. 

THE  LABORATORY  ASPECT  OF  THE  COURSE. 

The  course  will  continue  to  be  based  on  experiment,  the  amount  of 
laboratory  work  being  limited  only  by  the  physical  possibilities  of  the 
situation.  The  experiment  will  precede  the  class  discussion  in  order 
that  the  pupil  may  conceive  the  things  that  he  is  talking  about  as  reali- 
ties. Chemical  thinking  cannot  go  far  without  these  definite  concep- 
tions. It  requires  images  of  real  things,  and  it  is  this  point  of  view  that 
should  determine  the  character  of  our  laboratory  work.  There  seems 
to  be  considerable  difference  of  opinion,  if  not  confusion,  on  this  point. 

There  is  the  point  of  view  which  assumes  that  it  is  the  purpose  of  the 
experiment  to  prove  the  statement  of  the  teacher  or  the  text.  Because 
there  was  so  much  that  was  bad  in  reliance  upon  authority  in  older  types 
of  education,  it  is  felt  that  science  must  have  none  of  this,  but  must  ac- 
company everything  by  rigorous  proof.  Following  this  method  at  its 
worst,  the  pupil  is  stimulated  into  a  condition  of  perpetual  doubt.  He 
meets  every  statement  with  a  but,  and  has  rather  the  air  of  believing 
that  some  scientific  charlatanry  is  being  imposed  on  him.  This  is  wrong; 
science  does  not  have  this  attitude  of  perpetual  doubt.  It  requires  the 
most  rigorous  proof  from  discoverers  of  new  things,  but  if  each  of  us 
had  demanded  ocular  demonstration  at  each  step  in  our  advancing  knowl- 
edge, we  should  probably  still  be  somewhere  in  the  realm  of  descriptive 
inorganic  chemistry.  Moreover,  it  is  a  serious  scientific  mistake  to  let 
the  pupil  think  that  a  single  experiment  performed  under  the  ordinary 
condition  of  the  beginner's  laboratory  proves  much  of  anything.  If  it 
does,  the  speaker  has  seen  many  curious  things  proved  in  his  time.  Let 
us  be  frank:  these  experiments  show  at  best  the  line  of  thought  by  which 
the  proof  is  obtained.  They  illustrate  the  proof — they  do  not  give  it. 

Nor  does  the  theory  that  the  pupil  should,  in  the  laboratory,  rediscover 
the  fundamental  truths  of  the  science,  give  us  a  right  basis  for  experi- 
mental work.  Followed  to  the  extreme,  this  method  soon  reduces  itself 
to  an  absurdity.  Take,  for  example,  the  experiments  of  Lavoisier,  which 
afford  such  an  excellent  starting  point  in  the  teaching  of  the  subject. 
The  pupil  is  given  some  metals  and  a  balance,  and  is  supposed,  in  an  hour 
and  a  half,  to  rediscover  what  it  took  the  best  minds  the  world  then  pos- 
sessed several  centuries  to  accomplish.  The  fact  the  pupil's  laboratory 
record,  duly  attested  by  the  teacher,  indicates  that  he  independently 
accomplished  this  prodigious  feat  is  a  comment  on  the  system.  All  that 
is  done  in  this  method  at  its  best,  is  the  arousing  of  the  pupil's  curiosity, 
which  is  later  gratified  by  judicious^  suggestions  at  the  proper  moment 
from  the  teacher.  There  is  no  rediscovery;  the  line  of  thought  has  sim- 
ply been  retraced,  and  the  big  steps  have  ever  been  taken  by  the  teacher. 
To  be  a  discoverer  you  must  be  the  author  of  your  own  curiosity.  An- 
other trouble  with  this  method  is  that  once  committed  to  it  the  teacher 
is  driven  to  curious  round-about  expedients  to  prevent  the  pupil's  hav- 
ing knowledge  in  advance  of  the  thing  he  is  going  to  see.  lAhere  are 

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hundreds  of  instances  where  the  pupil  should  have  this  knowedge  in  ad- 
vance. 

The  speaker  is  more  and  more  convinced  that  while  the  laboratory 
should  to  a  certain  extent  seek  to  accomplish  the  things  which  the  hold- 
ers of  two  points  of  view  consider  desirable,  its  real  purpose  is  to  afford 
illustrative  material,  and  by  illustrative  material  he  means  that  which 
will  give  concrete  ideas — images — of  things  and  processes.  One  might 
read  hundreds  of  pages  about  chlorine,  but  if  he  had  never  seen  it  he 
would  never  know  it.  This  is  the  great  work  of  the  laboratory  method, 
to  teach  things  and  not  literal  symbols  for  them.  We  should  seek  this 
end,  and  let  other  considerations  give  way  to  it. 

And  we  shall  not  neglect  to  exercise  the  pupil's  scientific  imagination. 
Chemical  thinking  requires  this  faculty.  After  he  has  been  well  grounded 
in  the  method  of  the  laboratory,  we  shall  want  the  pupil  to  learn  to  fore- 
see chemical  possibilities.  The  progress  of  the  science  has  been  by  the 
working  together  of  experiment  and  imagination,  the  one  reacting  upon 
the  other  and  each  suggesting  in  turn  new  steps  in  the  advancing  knowl- 
edge. 

THE  CLASS-ROOM  ASPECT  OF  THE  COURSE. 

It  is  no  longer  being  framed  exclusively  for  the  college  entrance  re- 
quirement; our  course  will  not  require  us  to  cover  so  much  material  as 
it  did  formerly.  Discussion  of  the  rare  elements  and  their  compounds 
will  give  way  to  a  more  intensive  study  of  those  that  show  typical  chem- 
ical actions,  and  establish  the  main  lines  of  thought.  We  shall  prefer  to 
do  this  by  reference  to  the  things  of  the  practical  life  where  we  can,  but 
we  will  not  go  into  the  chemistry  of  foods,  dyes,  textiles  and  the  like, 
knowing  that  this  matter  is  far  too  complex  for  us  to  use  in  establishing 
the  laws  and  relationships  that  are  necessary  for  a  comprehension  of  the 
science.  We  shall  draw  from  every  aspect  of  chemistry  in  our  effort 
to  establish  the  principles  of  chemical  action.  Our  teaching  may  grow 
less  descriptive  and  more  dynamic.  We  may  find  it  better  to  study 
types  of  chemical  action  than  to  study  elements  and  compounds.  As 
suggestion  along  this  line,  we  might  proceed,  after  reaching  the  defini- 
tions of  chemical  action,  element  and  compound,  to  the  general  study  of 
simple  decompositions,  using  many  experimental  illustrations.  We  would 
bring  in  the  ideas  of  stability  and  heat  of  formation.  We  would  then 
proceed  to  direct  combinations,  simple  replacements,  and  so  on,  until 
finally  the  pupil  would  have  a  very  good  idea  of  the  comparatively  few 
types  of  chemical  action.  He  would  acquire  incidentally  a  very  prac- 
tical descriptive  knowledge. 

Our  course  will  necessarily  continue  to  pay  a  large  amount  of  atten- 
tion to  chemical  theories,  in  order  that  we  may  have  the  means  of  seeing 
analogies  and  interpreting  results.  The  mechanism  of  chemical  changes 
is  so  far  removed  from  direct  observation  by  the  senses  that  any  attempt 
to  comprehend  these  must  be  largely  by  aid  of  the  imagination.  The 
atomic  theory  has  given  us  a  splendid  instrument  for  this  purpose.  We 
should  retain  it  even  if  it  had  done  nothing  more  than  give  us  a  system  of 
chemical  formulas,  or  made  it  possible  to  represent  chemical  actions  by 
equations.  Only  one  who  has  attempted  to  teach  chemistry  without  the 
use  of  these  symbols  can  fully  appreciate  what  a  tremendous  aid  they 
are.  We  shall  therefore  want  to  establish  the  atomic  theory  rationally, 
and  to  show  how  formulas  are  determined.  This  is  perhaps  the  most 

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difficult  part  of  our  work,  but  the  fact  that  many  pupils  fail  utterly  to 
comprehend  this  matter  is  no  ground  for  its  omission  from  the  course. 
There  are  many  who  succeed,  and  we  must  not  forget  that  those  who  fail 
at  least  learn  that  such  knowledge  was  acquired  by  human  reasoning 
and  patient  experimenting.  We  should  make  our  pupils  feel  that  these 
theories  are  very  practical  things  indeed,  since  it  is  largely  by  their  aid 
that  the  science  has  advanced  and  brought  material  benefits  to  mankind. 

We  have  in  the  past  been  given  to  considerable  drill  in  certain  types  of 
chemical  problems,  largely  because  of  the  demands  of  college  entrance 
examinations.  There  has  been  a  good  deal  of  mental  gymnastics  in  the 
matter.  These  calculations  should  be  taught  in  a  less  formal  way;  the 
laboratory  is  the  best  place  to  do  it.  Let  the  pupil  calculate  from  the 
equations  the  quantities  of  substances  he  needs  for  his  reaction,  and 
then  actually  mix  them  in  these  proportions.  Let  him  get  practise  in 
correcting  gas  volumes  in  the  course  of  experiments  involving  simple 
gas  measurements.  Knowledge  acquired  in  this  way  has  a  far  greater 
staying  quality  than  that  obtained  in  formal  class-room  drill. 

As  we  have  already  said,  chemical  technology  will  find  a  place  in  the 
course,  but  it  must  be  taught  by  principle  too.  In  the  Solvay  process, 
for  example,  it  is  more  important  that  the  pupil  should  get  the  idea  of 
precipitation  by  differences  in  solubility  than  that  he  should  know  the 
mechanical  details  of  the  carbonating  towers.  It  is  more  important 
he  should  know  that  the  process  is  only  commercially  profitable  because 
the  ammonia  is  recovered,  thus  getting  hold  of  the  principle  of  the  utiliza- 
tion of  by-products,  than  that  he  should  know  the  factory  terms  for  the 
machinery  and  operations.  A  good  course  in  manufacturing  equip- 
ment, in  which  different  types  of  furnaces,  towers  and  the  like  were 
grouped  and  compared,  might  be  of  great  practical  and  educational  im- 
portance. But  isolated  bits  of  such  information  have  no  such  value. 

Our  high  school  chemistry  might  well  include  a  treatment  of  more 
organic  compounds  than  it  has  in  the  past.  This  knowledge  can  readily 
be  acquired  by  reference  to  inorganic  types.  So  many  of  the  simpler 
derivatives  of  the  hydrocarbons  are  things  of  every-day  life  that  in  order 
to  include  them  we  can  afford  to  sacrifice  some  of  the  things  of  the  tra- 
ditional elementary  course.  The  pupil  needs,  moreover,  some  intima- 
tion of  the  character  and  extent  of  the  organic  branch  of  the  science. 

In  conclusion,  the  speaker  feels  that  the  best  hope  for  the  improvement 
of  high  school  chemistry  lies  in  discussions  of  the  kind  we  are  engaged  in 
this  morning.  The  experimental  end  of  our  work  has  been  so  new  and 
interesting  that  much  of  our  time  has  been  spent  on  these  matters.  But 
the  time  is  at  hand  when  a  reconsideration  of  the  course  as  a  whole  in 
its  general  relations  would  be  of  benefit  to  the  teaching  of  the  elementary 
science.  JESSE  E.  WmTsiT. 

DKWITT  CLINTON  HIGH  SCHOOL, 
NEW  YORK  CITY. 


CHEMISTRY  IN  SECONDARY  SCHOOLS.1 

It  is  not  necessary  in  a  gathering  such  as  this  to  recount  the  stages  in 
the  history  of  chemistry  teaching  in  secondary  schools — how,  from  the 

1  Presented  at  the  second  decennial  celebration  of  Clark  University,  Worcester, 
Mass.,  September  16,  1909. 

130 


19 

purely  descriptive  natural  philosophy  of  the  early  college  we  finally  as- 
sayed the  teaching  of  chemistry  and  physics  as  sciences;  how  the  mis- 
cellaneous encyclopedic  instruction  has  been  replaced  by  courses,  de- 
signed, in  these  latter  days,  to  develop  power  for  the  pupil  rather  than 
to  impart  knowledge. 

The  changes  in  content  and  method  of  formal  secondary-school  instruc- 
tion have  been  brought  about  by  the  colleges;  by  advice,  by  supplying 
the  teachers  and  most  drastically,  by  the  requirements  for  admission. 
While  the  bulk  of  the  class  might  pass  from  the  school  and  not  be  heard 
from  again,  the  failure  of  a  pupil  to  pass  the  college  examination  is  quickly 
brought  home  to  the  teacher,  so  that  the  entrance  examinations  have 
become  the  standard  of  the  school. 

During  the  last  fifteen  years  four  syllabuses  have  been  published  which 
have  decidedly  affected  the  teaching  of  chemistry  in  schools;  in  1894 
that  of  the  Committee  of  Ten,  descriptive  and  general;  in  1898  a  Harvard 
syllabus,  largely  quantitative  and  scientific  in  method;  in  1900,  the 
syllabus  of  the  College  Entrance  Examination  Board,  a  plan  for  a  course 
I  hesitate  to  classify;  in  1905,  the  last  revision  of  the  syllabus  of  the  New 
York  Department  of  Education,  a  historico-systematic  course. 

There  is  almost  nothing  in  common  to  these  four  courses,  and  although 
the  College  Entrance  Examination  Board  maintains  and  strengthens  its 
hold  upon  the  schools  it  has  never,  fortunately  for  the  pupils,  conducted 
its  chemistry  examination  in  accordance  with  its  syllabus. 

If  we  examine  the  texts  to  find  what  is  being  taught  in  high  schools 
we  find  the  chemistry  text-books  to  be  descriptive  or  theoretical;  very  few 
have  successfully  combined  the  two.  The  descriptive  texts  usually 
become  encyclopedic,  try  to  include  all  the  elements,  strange  compounds, 
the  latest  processes  and  weird  discoveries,  often  curtailing  or  entirely 
displacing  those  common  things  we  are  too  liable  to  take  for  granted 
that  every  one  knows.  The  theoretic  texts  are  largely  the  product  of 
college  men.  These  tend  to  become  too  abstract  and  sacrifice  the 
pupil  to  the  subject.  One  elementary  text  of  very  wide  use  devotes 
two  pages  to  a  discussion  of  the  action  of  bleaching  powder,  but  does  not 
state  how  it  is  used  or  for  what  goods. 

If  a  subject  is  to  be  treated  as  a  science  many  facts  must  be  given 
and  understood  in  order  that  the  pupil  may  acquire  a  comprehensive 
idea  of  the  subject.  It  is  folly  to  expect  thorough  understanding  of  a 
part  without  a  general  knowledge  of  the  whole.  The  high  schools  can- 
not train  chemists  or  engineers.  Time  and  cost  do  not  admit  of  such 
intensive  science  teaching,  even  if  it  is  desirable.  Such  teaching  should 
be  left  to  the  college. 

If  we  take  the  pupils  as  we  find  them  in  our  large  city  high  schools 
they  are  not  well  informed  and  have  little  opportunity  to  be.  They 
live  in  a  complex  environment.  The  city  boy  or  girl  is  brought  in  con- 
tact with  but  few  simple  phenomena;  a  push  of  a  button — a  bell  is  rung; 
another  push — a  door  is  unlocked;  another  push — a  light  appears.  The 
modern  apartment  is  a  complicated  structure  operated  by  buttons. 
If  we  look  for  chemical  actions  within  this  pupil's  sphere  we  find 
them  to  be  rather  few,  too  familiar  to  hold  the  attention  or  too 
complicated  to  tempt  analysis.  He  comes  in  contact  with  but  few 
elements  and  but  few  pure  compounds.  Steel  is  to  him  a  specially 
pure  iron,  zinc  is  the  metal  used  in  batteries,  tin — used  for  cans, 


20 

sulphur  smells  bad.  He  has  often  been  told  that  soda  water 
contains  no  soda.  Soap  is  useful  in  cleaning,  as  it  eats  dirt  as  an  acid 
"eats  metal."  A  material  involving  electric  means  is  necessarily  superior. 
The  tendency  to  centralization  in  driving  our  small  industrial  estab- 
lishments has  narrowed  the  child's  opportunities  for  observation.  The 
shops  of  the  blacksmith,  carpenter  and  soap-maker  where  he  learned  the 
art  of  critical  observation  and  learned  some  things  not  taught  in  school 
have  been  withdrawn  behind  doors  marked  "no  admission." 

The  classes  of  our  large  schools  are  mixed  as  to  sex,  race  and  ability. 
It  is  often  said  with  pride  that  our  urban  population  is  cosmopolitan, 
but  that  the  second  generation  from  the  emigrant  is  acquainted  with 
American  ways.  Admitting  that  the  second  generation  may  be  some- 
what acquainted  with  American  ways,  we  must  also  admit  that  the 
population  of  our  large  cities  is  becoming  mongrel.  The  mongrel  is  never 
stable  and  is  rarely  successful.  The  psychology  of  the  mongrel  is  analogous 
to  that  of  the  mob.  Is  it  not  then  asking  too  much  that  children  of  one 
or  two  generations  from  barbarity  should  be  put  through  the  same  course 
and  be  expected  to  meet  the  same  educational  standards  as  the  natives 
of  Massachusetts? 

The  tendency  of  education  at  present  is  the  development  of  power, 
of  ability  to  reason,  to  think.  We  may,  indeed,  ask  if  the  drill  along 
this  line  has  not  been  pushed  so  far  at  times  as  to  neglect  giving  some- 
thing to  think  about.  The  school,  unlike  the  college,  works  by  the  clock, 
the  work  must  be  cut  to  fit  the  time,  thus  we  often  find  a  few  facts  or 
questions  are  presented  in  such  a  way  that  but  one  conclusion  is  possible. 
This  is  called  inductive  teaching — teaching  to  reason. 

It  makes  the  work  easier  for  the  teacher  if  the  work  can  be  made  to 
follow  a  mathematical  model,  so  problems  come  to  take  an  important 
place.  The  work  becomes  quantitative  and  is  now  held  to  develop 
thought,  originality  and  logical  reasoning.  But  the  problem  in  ele- 
mentary chemistry  is  usually  of  type  form,  and  is  not  the  teacher  largely 
sponging  on  the  power  drilled  into  the  pupil  by  the  mathematics  teacher? 
The  English  of  the  schools  is  criticized  by  college  and  business  men  alike. 
I  believe  a  clear,  concise  exposition  of  phenomena  in  correct  language 
will  be  of  more  benefit  to  the  pupil  than  any  number  of  problems  in 
chemical  arithmetic. 

The  pupils  I  have  in  mind  are  the  ordinary  ones  in  large  schools,  thir- 
teen to  sixteen  years  of  age,  girls  and  boys.  Only  a  small  percentage  will 
go  to  college,  some  will  go  to  business,  some  to  be  clerks,  some  home 
makers,  some  teachers.  They  have  been  herded  in  elementary  schools 
taught  at  in  bulk.  They  are  deficient  in  English  and  any  correct  notions 
of  the  activities  of  the  world.  It  is  the  business  of  the  high  school  to 
supplement  the  elementary  school  and  by  its  specialization  correct  the 
errors  of  the  grades  and  systematize  the  instruction.  College  prepara- 
tion is  only  incidental. 

A  large  amount  of  knowledge  is  not  needed  in  practical  life  so  much 
as  the  power  to  do  things,  but  knowledge  certainly  increases  power. 
While  we  must  be  able  to  do  one  thing  well  even  a  superficial  knowledge 
of  many  things  is  not  to  be  despised.  Good  judgment,  ability  to  arrive 
at  accurate  conclusions  from  given  data  is  most  essential,  but  if  we  look 
closely  a  large  part  of  what  is  commonly  called  reasoning  is  but  rehearsing 
of  formulae.  Good  judgment  cannot  be  taught.  So  few  of  our  pupils 

132 


21 

will  ever  be  so  situated  that  they  need  reason  independently  concerning 
chemical  phenomena  that  it  is  scarcely  justifiable  to  foist  the  time  and 
cost  of  such  instruction  on  the  public. 

Where  and  how  can  chemistry  accomplish  the  most  good  in  the  school? 
If  the  object  of  education  is  to  develop  a  youth  most  completely,  to  make 
a  well-rounded  individual,  to  make  him  feel  an  intelligent  interest  in  the 
activities  of  the  world,  it  is  not  necessary  that  each  factor  in  such  a  total 
should  be  well  rounded.  A  number  of  smooth,  well-rounded  sticks  will 
make  a  very  insecure  bundle,  but  if  some  of  the  tricks  are  somewhat 
rough  the  bundle  may  not  appear  so  elegant  but  it  will  be  more  firm. 
Chemistry  touches  every  phase  of  human  activity.  It  requires  language 
for  its  expression,  mathematics  for  its  determination,  physics  for  its 
operation.  Its  history  is  the  history  of  the  world. 

It  would  be  impossible  to  find  a  better  subject  than  chemistry  to  bind 
together  the  school  work,  to  systematically  furnish  splinters  to  make 
the  bundle  strong.  The  domestic  science  teacher,  the  biology  teacher 
and  the  physics  teacher  give  some  splinters  of  information  which  they 
call  chemistry  and  build  their  work  upon  this  basis,  usually  indigestible 
definitions.  A  systematic  course  in  elementary  science  should  be  placed 
in  the  first  year  of  the  high  school,  designed  to  impart  that  information 
of  things  and  processes  we  might  well  expect  every  one  to  know.  This 
might  be  followed  later  by  a  course  more  thorough. 

We  now  expect  our  pupils  to  specialize  as  soon  as  they  leave  the  ele- 
mentary schools  and  to  prepare  for  some  life  work.  He  or  she  knows 
nothing  of  human  activities  out  in  the  every-day  world ;  there  is  practic- 
ally no  place  in  the  school  curriculum  where  this  is  taught.  We  have 
trade  schools,  vocation  schools,  commercial  schools,  not  to  mention 
others  all  of  which  require  him  to  specialize  before  showing  him  any 
general  plan  from  which  to  choose  or  guiding  his  choice. 

The  pupil  who  will  receive  no  further  school  instruction  can  in  a  year 
be  given  a  good  knowledge,  by  a  teacher  with  adequate  equipment,  of 
many  of  the  facts  of  elementary  chemistry  relating  to  our  daily  life  and 
its  activities — a  knowledge  sufficient  in  most  cases  to  excite  a  lasting 
interest  in  natural  phenomena  and  to  cause  the  student  to  seek  explana- 
tion. There  is  a  multitude  of  chemical  facts  which  concern  the  boy 
who  goes  into  the  shop  or  office  or  behind  the  counter,  and  which  he 
should  know.  The  girl  who  will  stop  at  home  or  teaches  others'  chil- 
dren is  also  concerned  with  chemical  phenomena,  chemical  information 
which  has  been  crowded  out  of  her  curriculum  to  make  room  for  more 
cultured  and  less  mussy  subjects. 

Adhering  to  traditional  procedure,  our  science  courses  have  become 
pseudotheoretical  or  pseudotechnical ;  it  is  time  we  had  one  systematically 
informational  and  practical.  Facts  are  as  important  as  explanations 
and  should  precede  them.  Such  a  course  need  not  pretend  complete- 
ness in  any  line.  It  might  be  comparative  rather  than  critical.  It  would 
not  attempt  to  rediscover  or  verify  natural  laws,  but  would  aim  to  culti- 
vate the  powers  of  observation  and  of  accuracy  of  description,  to  express 
ideas  of  phenomena  in  simple,  direct  English  rather  than  to  hide  incoherent 
thought  behind  a  big  name  or  a  slang  expression. 

In  a  first  course  in  chemistry,  atoms,  molecules,  ions  and  many  other 
terms  might  be  omitted  altogether.  They  are  but  words,  the  modern 
idea  of  an  atom  is  incomprehensible  to  one  without  a  wide  knowledge  of 
chemistry.  Theory  should  be  eliminated  as  much  as  possible,  making 

133 


22 

the  course  treat  of  facts,  their  sequence  and  relation  to  one  another. 
Numerical  problem  solving  should  take  but  a  small  part  in  recitation 
work.  No  more  can  come  out  of  an  equation  than  we  put  into  it.  It 
cannot  develop  originality. 

Such  a  course  for  children  of  twelve  to  thirteen  years  would  need  sim- 
plicity in  its  treatment.  Faraday's  lectures  to  children  are  a  model  in 
this  respect.  Ostwald's  "Conversations"  show  how  some  complicated 
things  may  be  dealt  with  simply. 

I  would  have  such  a  course  give  information  concerning  natural  phe- 
nomena and  the  work  of  man,  show  what  is  being  done,  and  how,  with- 
out technical  detail. 

I  would  give  the  pupil  something  to  know.  Facts  that  are  worth  know- 
ing in  and  of  themselves — facts  that  concern  himself,  his  food,  his  cloth- 
ing, his  shelter  and  his  work.  Concerning  the  things  he  or  she  will  meet 
in  life,  no  matter  whether  the  future  be  as  a  chemist,  a  bookkeeper  or  in 
the  kitchen.  The  material  is  ample. 

The  subject  might  be  systematized  by  its  applications  rather  than 
the  traditional  order.  Study  topics  rather  than  elements;  study  deter- 
gents, not  soap;  study  bleaching  rather  than  peroxide  or  bleaching  pow- 
der. The  development  of  the  race  through  the  stone,  bronze  and  iron 
age  has  depended  largely  upon  his  chemical  knowledge.  Let  us  study 
the  metals  in  their  metallic  aspects  rather  than  according  to  the  periodic 
table. 

Foods,  clothing,  materials  of  utility  and  convenience  or  of  commerce 
often  can  not  be  rationally  treated  by  the  present  systems  of  our  texts, 
but  a  suitable  systematization  might  easily  include  these ;  what  they  are, 
how  they  are  produced  and  what  they  do. 

In  its  effects  upon  the  pupil  and  school,  we  may  be  sure  that  pupils 
who  have  seen  something  of  the  general  trend  of  the  instruction  through 
a  systematic  preliminary  course  will  feel  more  interest  to  continue  study 
and  will  accomplish  more  and  better  work  in  later  courses. 

MICHAEL  D.  SOHON. 

MORRIS  HIGH  SCHOOL, 
NEW  YORK,  N.  Y. 


134 


RADIOACTIVITY.1 

BY  ANDRE  DEBiERNE.2 
Received  July  i,  1911. 

Radioactivity  comprises  to-day  a  very  large  number  of  facts  and  theo- 
ries of  which  it  would  not  be  possible  to  give  a  complete  survey  in  a  brief 
address.  Nevertheless,  I  shall  make  an  effort  to  bring  out  all  the  chief 
points  of  interest  of  the  new  science,  the  birth  of  which  may  be  consid- 
ered without  exaggeration  as  the  most  important  scientific  event  of  the 
past  few  years. 

Not  only  has  this  new  science  revealed  the  existence  of  extremely  curious 
substances  and  brought  a  rich  harvest  of  new  natural  phenomena,  but 
it  has  led  us  to  the  attack  of  a  problem  which  seemed  absolutely  chimer- 
ical only  a  few  years  ago — the  problem  of  the  transmutation  of  atoms 
or  of  the  chemical  elements;  for  it  is  now  demonstrated  that  the  phe- 
nomena of  radioactivity  are  concomitants  of  the  disintegration  of  atoms. 
Radioactivity  may  now  be  defined  as  the  science  of  atomic  transforma- 
tions; it  is  not  impossible  that  in  time  radioactivity  may  become  the  art 
of  changing  chemical  elements  into  one  another.  The  facts  known  at 
present  leave  no  doubt  as  to  the  reality  of  atomic  disintegrations;  if  as 
yet  these  transformations  are  entirely  beyond  our  control,  possibly  some 
day  we  may  learn  how  to  bring  them  about  and  to  control  them. 

The  fundamental  phenomenon,  which  was  discovered  by  Henri  Bec- 
querel  and  has  served  as  the  point  of  departure  for  the  development  of 
radioactivity,  is  as  follows:  Certain  substances  emit  spontaneously  a 
peculiar  radiation  whose  properties  are  analogous  to  those  of  the  rays 
obtained  in  a  Crookes  tube.  The  new  rays  render  gases  conductors  of 
electricity,  act  on  a  photographic  plate,  and  produce  fluorescence  in  certain 
substances.  This  spontaneous  emission  of  rays  was  first  observed  in  the 
case  of  uranium  and  its  compounds,  later  also  in  the  case  of  thorium  com- 
pounds. Then  were  discovered  new  substances  possessing  the  same 
property  in  a  very  high  degree.  All  these  substances  are  said  to  be 
radioactive.  They  constitute  a  new  source  of  energy. 

An    apparently    essential  characteristic  of  the  phenomenon  of  radio- 

1  A  summary  presented  at  the  Second  Decennial  Celebration  of  Clark  University, 
Worcester,  Mass.,  September  17,  1909. 

2  Translated  from  the  French  by  M.  A.  Rosanoff. 

135 


1389  RADIOACTIVITY. 

activity  is  its  spontaneity :  the  emission  of  rays  takes  place  without  visi- 
ble external  cause.  This  characteristic  permits  of  distinguishing  the 
phenomena  of  radioactivity  from  those  that  take  place  in  the  course  of 
certain  chemical  reactions.  For  instance,  the  oxidation  of  phosphorus 
is  accompanied  by  phosphorescence  and  by  electrical  conductivity  of  the 
gases  surrounding  the  phosphorus.  The  same  phenomena  may  be  brought 
about  by  the  action  of  heat  upon  the  sulfate  of  quinine.  But  in  all  such 
cases  the  phenomenon  is  not  spontaneous ;  it  is  brought  about  by  external 
causes  which  are  easy  to  detect.  Therefore,  phosphorus  and  quinine 
sulfate  are  not  considered  as  radioactive  substances. 

Another  essential  characteristic  was  brought  out  by  the  early  researches 
of  Madame  Curie.  Radioactivity  is  an  atomic  property.  The  spon- 
taneous emission  of  rays  is  connected  with  the  radioactive  atom,  and  is 
not  in  the  slightest  degree  influenced  either  by  changes  of  state  of  aggre- 
gation of  by  chemical  combination  with  the  atoms  of  other  elements. 
Thus,  the  intensity  of  the  Becquerel  rays  emitted  by  the  substances  con- 
taining uranium,  and  measured  by  the  conductivity  of  the  surrounding 
gases,  is  always  proportional  to  the  number  of  uranium  atoms  contained 
in  the  substance  and  is  independent  of  the  form  in  which  uranium  may 
be  present.  Among  the  numerous  other  properties  of  matter,  mass  alone 
is  so  distinctly  atomic  in  its  nature. 

Our  realization  of  the  atomic  character  of  the  radioactive  property  has 
had  a  directing  influence  on  the  science  of  radioactivity  and  has  led  to 
the  establishment  of  its  present  theories.  But  first  of  all  it  had  led  to 
the  discovery  of  radium  itself  and  of  the  other  strongly  radioactive  sub- 
stances. I  shall  review  briefly  the  genesis  of  the  discovery  of  radium, 
which  forms  one  of  the  most  beautiful  investigations  ever  carried  out 
in  the  physical  sciences,  both  as  regards  the  logical  keenness  with  which 
the  research  was  carried  on  and  as  regards  the  material  difficulties  which 
had  to  be  overcome.  The  novel  method  employed  has  since  been  con- 
stantly used  in  researches  in  radioactivity. 

Among  the  elements  that  had  previously  been  known,  only  uranium 
and  thorium  were  radioactive,  and  the  activity  of  any  substance  con- 
taining one  of  these  elements  was  found  to  be  proportional  to  the  quan- 
tity of  the  active  element  present.  Certain  minerals,  however,  contain- 
ing uranium  showed  a  greater  activity  than  metallic  uranium  itself. 
Pierre  Curie  and  Madame  Curie,  thoroughly  convinced  of  the  atomic 
nature  of  radioactivity,  assumed  that  these  minerals  contained  new 
chemical  elements,  endowed  with  greater  activity  than  uranium,  and  al- 
though physicists  by  profession,  and  with  only  rudimentary  laboratory 
means  at  their  disposal,  they  undertook  a  search  after  the  new  hypo- 
thetical elements. 

I  cannot  depict  here  all  the  difficulties  that  presented  themselves  in  the 
search,  which  involved  the  chemical  treatment  of  tons  of  material.  Suffice 
it  to  recall  the  results  obtained  by  Pierre  Curie  and  Madame  Curie  after 
several  years  of  uninterrupted  effort.  Those  results  fulfilled  their  expec- 
tations entirely.  The  minerals  studied  do  contain  strongly  radioactive 
compounds,  whose  radioactivity  is  due  to  the  presence  of  new  chemical 
elements.  In  the  case  of  one  of  these  elements,  namely  radium,  it  has 
been  possible  to  prepare  a  series  of  pure  salts;  further,  its  spectrum  has 
been  studied,  its  atomic  weight  determined  and  a  place  has  been 

136 


GENERAL,    PHYSICAL  AND  INORGANIC.  1390 

assigned  to  it  in  the  periodic  classification  of  the  elements.  Radium  has 
become  a  marvelous  instrument  of  research,  and  to  it  we  owe  all  the 
most  important  discoveries  in  radioactivity. 

It  was  soon  recognized  that  radioactive  substances  may  differ  from 
one  another,  not  only  in  intensity  of  radiation,  but  also  in  the  character 
of  radiation  and  in  certain  peculiarities  in  the  mode  of  emission  of  the 
rays.  On  the  basis  of  these  properties  it  is  as  easy  to  recognize  a  given 
radioactive  element  with  certainty  as  it  is  to  recognize  one  of  the  older 
elements  with  the  aid  of  spectrum  analysis. 

The  principal  new  radioactive  substances  are  polonium  and  radium, 
discovered  by  Pierre  Curie  and  Madame  Curie;  actinium,  discovered  by 
myself  shortly  afterwards;  radio-thorium,  discovered  by  Hahn;  and 
ionium,  discovered  by  Rutherford  and  Boltwood.  However,  certain 
of  these  substances  are  really  complex  mixtures  containing  entire  fami- 
lies of  chemical  elements:  namely,  the  thorium  family,  the  radium  family, 
and  the  actinium  family. 

The  rays  emitted  by  radioactive  substances  may  be  subdivided  into 
three  groups,  viz.,  the  a  rays,  the  /?  rays,  and  the  ?  rays,  which  are  analo- 
gous to  the  three  groups  of  rays  emitted  in  a  Crookes  tube,  viz.,  canal 
rays,  cathode  rays,  and  Roentgen  rays.  The  a  rays  are  constituted  by 
the  projection  of  positively  charged  particles ;  the  ft  rays  by  a  projection 
of  negatively  charged  particles;  the  f  rays  are  not  charged  at  all. 

The  particles  of  /?  rays  are  electrons,  and  the  rays  are  easily  bent  out  of 
their  path  by  a  magnetic  field.  Certain  /?  rays  are  constituted  by  elec- 
trons projected  with  an  extremely  great  velocity,  a  velocity  approach- 
ing that  of  light,  and  it  has  been  possible  to  verify  on  these  rays  an  im- 
portant deduction  from  the  electron  theory.  For  very  great  velocities, 
namely,  the  inertia  of  a  particle  ceases  to  be  a  fixed  quantity;  it  may 
greatly  increase  with  increased  velocity  of  motion,  and  so  the  particle  no 
longer  obeys  the  laws  of  Newtonian  mechanics.  Finally,  comparing 
(3  rays  and  cathode  rays,  one  finds  them  analogous,  only  the  particles  of 
ft  rays  move  with  greater  velocity  and  are  capable  of  penetrating  a  much 
thicker  layer  of  matter  (for  instance,  a  plate  of  aluminium  one  mm. 
thick). 

The  a  rays  are  constituted  by  the  projection  of  material  particles, 
charged  electro-positively,  having  the  dimensions  of  atoms,  and  moving 
with  a  smaller  velocity  than  the  particles  of  /?  rays.  The  a  rays  are  bent 
by  a  magnetic  field  with  considerable  difficulty,  and  can  penetrate  only 
a  very  thin  layer  of  matter  (aluminium  foil  V20  mm.  thick  absorbs  them 
completely).  They  have  the  peculiarity  of  suddenly  stopping  after 
having  traversed  a  certain  well-determined  path  in  a  given  medium. 
The  length  of  this  path  in  air  is  a  very  important  quantity,  for  it  permits 
of  distinguishing  from  one  another  the  different  species  of  a  rays  and 
consequently  also  the  different  radioactive  substances.  The  a  particles 
play  a  very  important  part  in  radioactive  transformations,  and  their 
nature  seems  now  to  be  clearly  understood. 

The  f  rays  are  not  charged,  and  therefore  are  not  deflected  by  a  mag- 
netic field.  They  suffer  but  slight  absorption  in  matter  (a  considera- 
ble proportion  of  the  7-  rays  from  radium  passes  through  a  lead  plate 
one  centimeter  in  thickness). 

These  several  rays  excite  fluorescence  in  a  number  of  substances  (platino- 

137 


1391  RADIOACTIVITY. 

cyanide  of  barium,  sulfide  of  zinc,  uranyl  salts,  glass,  paper,  diamond, 
etc.).  The  action  of  a  rays  upon  zinc  sulfide  produces  the  very  peculiar 
phenomenon  generally  designated  by  the  term  scintillation;  in  this,  the 
luminosity  of  the  zinc  sulfide  screen  is  caused  by  an  infinity  of  brilliant 
little  points  which  appear  and  disappear  continually  and  which  are  clearly 
distinguishable  when  the  screen  is  examined  with  a  lens. 

The  radioactive  substances  constitute  a  new  source  of  energy ;  but  dur- 
ing the  earlier  researches  both  the  origin  and  the  mechanism  of  this  pro- 
duction were  entirely  unknown.  Pierre  Curie  and  Madame  Curie  ad- 
vanced two  distinct  hypotheses  to  explain  the  production  of  this  energy. 
The  first  hypothesis  assumed  that  the  energy  was  furnished  from  outside 
in  the  form  of  a  special  radiation,  causing  in  the  radioactive  substances 
a  phenomenon  analogous  to  phosphorescence.  According  to  the  second 
hypothesis,  the  energy  comes  from  the  active  substance  itself,  and  hence 
the  emission  of  energy  must  be  accompanied  by  a  change  in  the  substance. 
Pierre  Curie  and  Madame  Curie,  who  had  demonstrated  the  atomic  char- 
acter of  the  new  property,  believed  thoroughly,  even  before  radium  had 
been  discovered,  that  the  transformation  takes  place  in  the  radioactive 
atom  itself,  which  must  therefore  change  into  a  different  atom  and,  con- 
sequently, gradually  disappear  in  course  of  time.  It  is  this  hypothesis  of 
atomic  transmutation  that  has  proved  to  be  most  fruitful  and  has  formed 
the  basis  of  the  theories  accepted  at  present. 

The  principal  fact  which  has  led  to  these  theories  is  as  follows:  With 
the  aid  of  radioactive  substances,  whose  activity  appears  constant  and 
permanent,  it  is  possible  to  produce  phenomena  of  radioactivity  whose 
intensity  diminishes  in  time.  These  phenomena  of  temporary  activity 
may  be  observed  under  various  circumstances.  Thus,  if  any  substance 
whatever  is  placed  near  a  salt  of  radium,  thorium,  or  actinium,  the  sur- 
face of  the  substance  becomes  radioactive,  and  this  activity  diminishes 
more  or  less  rapidly  in  time.  This  is  the  phenomenon  of  induced  radio- 
activity discovered  by  Pierre  Curie  and  Madame  Curie.  Similarly,  any 
gaseous  atmosphere  surrounding  radium,  thorium,  or  actinium,  becomes 
itself  radioactive,  and  its  activity  likewise  diminishes  in  time.  Ruther- 
ford, the  discoverer  of  this  last  phenomenon,  gave  the  name  "emana- 
tion" to  the  cause  of  the  temporary  activity  of  the  gases.  Finally,  as 
first  observed  by  myself,  in  the  case  of  actinium,  substances  temporarily 
radioactive  may  also  be  obtained  through  certain  chemical  separations 
in  mixtures  containing  permanently  radioactive  substances. 

These  temporary  radioactivities  often  follow  complex  laws  of  de- 
crease. The  study  of  these  laws  has  shown  that  there  exist  really  several 
different  kinds  of  radioactivity  succeeding  one  another  in  time.  When 
one  kind  of  activity  has  died  out,  another  replaces  it,  and  this  may  grad- 
ually cease  to  exist  in  its  turn.  Each  kind  of  radioactivity  is  character- 
ized by  its  own  velocity  of  decrease  and  by  a  radiation  peculiar  to  itself. 
Extraordinarily  great  temporary  radioactivities  may  accumulate  in  an 
extremely  slight  quantity  of  matter. 

Applying  to  these  temporary  radioactivities  the  idea  which  had  guided 
to  the  discovery  of  radium,  namely,  that  radioactivity  is  an  atomic  prop- 
erty of  the  elements  exhibiting  it,  one  is  led  to  think  that  the  temporary 
radioactivities  which  have  been  separated  from  radium,  thorium,  and 
actinium  characterize  new  radioactive  atoms.  And,  accepting  the 

138 


,    PHYSICAL   AND    INORGANIC.  1392 

hypothesis  of  atomic  transmutation  as  an  explanation  of  the  origin  of 
radioactive  energy,  the  decrease  of  a  given  radioactivity  appears  to  re- 
sult from  the  gradual  disappearance  of  a  radioactive  element  and  its 
transmutation  into  another  element. 

The  present  theory  of  radioactive  phenomena  is  based  on  these  con- 
siderations. It  was  proposed  by  Rutherford  and  Soddy,  who  have 
published  numerous  observations  in  complete  accord  with  it.  At  pres- 
ent the  theory  is  accepted  by  all  investigators  of  radioactivity.  An 
extremely  precious  guide  in  research,  it  has  again  and  again  been  con- 
firmed by  discoveries  of  great  importance. 

The  various  phenomena  exhibited  by  radium  may,  then,  be  interpreted 
as  follows :  The  radium  atom,  which  emits  a  certain  a  radiation,  produces 
continually  a  radioactive  emanation.  This  emanation  is  considered 
to  be  a  radioactive  gaseous  element  resulting  from  the  transmutation 
of  radium,  and  hence  the  latter  must  gradually  disappear  in  time.  The 
emanation  emits  an  a  radiation  different  from  that  of  radium  and  disap- 
pears quite  rapidly  (the  decrease  follows  a  simple  exponential  law  and 
amounts  to  one-half  in  3.8  days).  The  emanation  produces  deposits  of 
induced  radioactivity,  which  are  considered  as  new  elements  resulting 
from  the  transmutation  of  the  emanation.  In  these  deposits  it  has  been 
possible  to  identify  a  series  of  stages  which  have  received  the  names  of 
Radium  A,  Radium  B,  Radium  C,  and  which  succeed  one  another,  radium 
A  changing  into  radium  B,  which  in  turn  changes  into  radium  C.  These 
different  members  of  the  group  emit  different  radiations  and  undergo  de- 
struction with  considerable  velocities. 

Following  radium  C  is  another  sequence  of  terms,  characterized  by  a  much 
smaller  rate  of  disappearance,  viz.,  Radium  D,  Radium  Et,  Radium  E2, 
and  Radium  F.  The  last-named  has  been  shown  by  Rutherford  to  be 
identical  with  polonium.  Polonium  itself  disappears  little  by  little,  but 
the  element  succeeding  it  is  as  yet  unknown. 

It  has  been  possible  to  determin  with  much  precision  the  laws  of  forma- 
tion and  destruction  of  the  different  transition  terms  of  the  series.  These 
laws  are  exponential  expressions  analogous  to  those  which  hold  for  mono- 
molecular  chemical  reactions.  Most  of  the  terms  have  been  isolated 
(by  means  of  chemical  reactions,  electrolysis,  heating,  condensation  at 
low  temperatures,  etc.),  and  the  several  exponential  formulas  followed  by 
their  rates  of  destruction  have  been  determined  separately,  the  formula 
corresponding  to  each  term  having  a  characteristic  exponent,  X,  of  its 
own.  The  rate  of  destruction  of  a  given  term  is  frequently  characterized 
by  specifying  the  time  T  required  to  diminish  by  one-half  the  original 
intensity  of  its  radiation.  The  quantity  i/^  may  be  considered  as  the 
mean  duration  of  life  of  an  atom  of  the  substance  under  consideration; 
it  is  denoted  by  the  symbol  0  and  is  usually  referred  to  briefly  as  "the 
mean  life."  We  have,  then,  0  =  i/k  and  T  =  @hi2. 

The  numerous  researches  which  have  been  carried  out  on  radioactive 
substances  have  resulted  in  fairly  complete  knowledge  concerning  the 
series  of  radioactive  transformations  in  the  several  families,  the  proper- 
ties of  the  different  terms,  and  the  properties  of  the  rays  emitted  during 
the  transformations.  The  knowledge  gathered  up  to  the  present  time  is 
reproduced  in  the  accompanying  tables. 

139 


1393 


RADIOACTIVITY. 


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143 


1397  RADIOACTIVITY. 

The  inter-relation  between  the  different  terms  of  one  and  the  same 
family  is  not  the  result  of  theoretical  interpretation.  It  is  a  thoroughly 
established  experimental  fact.  According  to  present-day  theory,  each 
term  represents  a  certain  chemical  element  which  differs  from  the  ordi- 
nary elements  only  by  its  ephemeral  existence  and  by  its  emitting  a  special 
radiation.  The  disappearance  of  the  radioactive  atom  is  the  result  of  its 
transformation  into  another  atom,  the  special  radiation  representing 
the  energy  which  accompanies  that  transformation.  According  to  this 
theory,  then,  the  study  of  radioactivity  has  led  to  the  discovery  of  some 
thirty  new  elements. 

The  theory  outlined  above  permits  of  an  easy  interpretation  of  all 
phenomena  thus  far  known.  Still,  it  was  a  matter  of  great  importance  to 
obtain  a  direct  experimental  demonstration  of  the  reality  of  atomic 
transformations,  and  of  the  existence  of  chemical  atoms  having  a  very 
short  life,  corresponding  to  the  ephemeral  radioactivities.  Such  direct 
experimental  demonstrations  have  actually  been  produced,  and  hence 
the  theory  rests  on  an  extremely  solid  basis. 

The  reality  of  atomic  transformations  accompanying  the  phenomena  of 
radioactivity  has  been  demonstrated  by  the  experiments  of  Ramsay 
and  Soddy  on  the  production  of  helium  from  radium.  Radium,  whose 
character  as  a  chemical  element  is  established  by  its  chemical  properties, 
by  its  atomic  weight,  and  by  its  spectrum,  continually  produces  the  gas 
helium,  which  is  itself  a  well  characterized  chemical  element.  This  pro- 
duction of  helium  cannot  be  reasonably  interpreted  in  any  other  way 
than  by  recognizing  atomic  transformation. 

Some  time  after  Ramsay  and  Soddy,  I  showed  that  the  same  phenom- 
enon takes  place  in  actinium,  which  also  continually  produces  helium 
gas.  Recently,  Soddy  has  discovered  the  production  of  helium  also 
from  uranium  and  from  thorium. 

The  production  of  helium  from  radioactive  substances  is  the  first 
case  ever  discovered  of  the  transformation  of  chemical  atoms. 

That  an  ephemeral  radioactivity  is  due  to  the  existence  of  a  corre- 
sponding chemical  element  has  been  experimentally  demonstrated  in 
the  case  of  the  radium  emanation.  This  emanation  has  been  isolated 
in  a  pure  state,  its  spectrum  determined,  and  its  volume  measured. 
Somewhat  numerous  experiments  were  first  carried  out  by  Ramsay 
and  his  collaborators,  and  though  the  published  results  are  not  in  per- 
fect agreement,  they  still  leave  no  doubt  whatever  as  to  the  material 
existence  of  the  emanation,  which  is  characterized  by  a  spectrum  of  its 
own.  The  isolation  of  the  substance  was  effected  by  utilizing  its  property 
of  easily  condensing  at  low  temperatures.  These  experiments  were  later 
repeated  by  Rutherford  and  Royds,  who  obtained  agreeing  measure- 
ments of  the  volume  occupied  by  the  pure  emanation  produced  by  a  given 
quantity  of  radium,  and  who  described  completely  the  spectrum  of  the 
emanation.  Recently,  I  have  carried  out  analogous  experiments:  my 
volume  measurements  agree  perfectly  with  Rutherford's,  and  my  spectro- 
photographs  are  identical  with  those  of  Rutherford  and  Royds.  I  have 
observed  besides  that  the  volume  of  gas  produced  does  not  increase  pro- 
portionally to  the  time,  owing  to  the  spontaneous  destruction  of  the 
substance.  The  observed  volume  is  invariably  proportional  to  the  radio- 
activity of  the  emanation,  no  matter  what  the  duration  of  its  produc- 
tion from  radium.  In  the  experiments  mentioned  above,  all  investiga- 

144 


GENERAL,    PHYSICAL  AND   INORGANIC.  1398 

tors  have  observed  the  production  of  helium  from  the  emanation:  the 
spectrum  of  helium  gradually  appears,  while  that  of  the  emanation  dis- 
appears. Finally,  Rutherford,  and  also  Ramsay,  have  succeeded  in  de- 
termining the  point  of  liquefaction  and  the  point  of  solidification  of  the 
emanation. 

It  thus  appears  entirely  certain  that  the  emanation  is  a  material  gas — 
a  fact  which  corroborates  very  strongly  Rutherford  and  Soddy's  theory. 

The  production  of  helium  by  radioactive  substances  is  directly  rela- 
ted to  the  emission  of  a  particles,  and  the  hypothesis  early  advanced 
by  Rutherford,  that  each  a  particle  is  an  atom  of  helium,  is  to-day  con- 
firmed. In  fact,  Rutherford  has  shown  that  the  a  rays  and  the  helium 
produced  by  the  radium  emanation  pass  through  thin  layers  of  matter 
in  a  similar  manner.  Other  properties  of  the  a  particles  are  in  complete 
accord  with  this  conception  of  their  nature. 

Now,  if  we  assume  that  in  all  transformations  accompanied  by  the 
emission  of  a.  particles  each  radioactive  atom  changes  into  the  next  in 
order  by  loss  of  a  single  a  particle  or  helium  atom,  it  becomes  possible 
to  calculate  the  atomic  weights  of  the  several  transition  elements  of  the 
radium  series.  The  atomic  weight  of  helium  being  4,  we  have,  namely: 
Radium  226.5  — >  Emanation  222.5  — >  Radium  A  218.5  — *• 
Radium  B  214.5  — >  Radium  C  214.5  — >  Radium  D  210.5  — > 
Radium  E  210. 5  — >  Radium  F,  or  Polonium,  210. 5  — >  a  last  unknown 
substance  206.5.  This  las*  number  represents  exactly  the  atomic  weight 
of  lead,  which  suggests  the  idea  that  this  element  is  the  final  product 
of  the  transformation  of  radium.  It  is  probable  that  this  idea  can  be 
subjected  to  experimental  verification. 

The  mother  substances,  uranium,  radium,  actinium,  and  thorium, 
ought  to  gradually  disappear  in  course  of  time,  as  they  are  transformed 
into  other  elements.  But  the  destruction  is  certainly  very  slow,  and  no 
diminution  of  their  activity  has  been  directly  detected.  The  laws  of 
their  destruction  may,  however,  be  determined  indirectly.  Since  the 
transformation  of  each  radioactive  atom  produces  an  emission  of  rays, 
it  is  natural  to  assume  that  the  more  intense  the  radiation  produced  by 
a  gram-atom  of  the  substance,  the  more  rapid  is  the  transformation. 
Thus,  radium  ought  to  have  a  much  shorter  life  than  uranium  or  thorium. 
The  comparison  of  the  radiations  may  be  carried  out  quantitatively, 
and  thus  the  ratio  of  the  mean  lives  of  two  radioactive  substances  may 
be  readily  obtained. 

On  the  other  hand,  if  it  is  assumed  that  the  emission  of  a  single  a  par- 
ticle corresponds  to  the  transformation  of  a  single  atom,  it  will  suffice 
to  determin  the  number  of  particles  emitted  per  second  by  a  given  mass 
of  the  active  substance  under  consideration,  in  order  to  ascertain  its 
velocity  of  transformation.  Indirect  determinations  were  first  made  by 
measuring  the  total  positive  charge  emitted  in  the  form  of  a  rays  by  the 
active  substance  and  making  an  assumptiion  concerning  the  charge  of  a 
single  particle.  The  results  so  obtained  have  been  confirmed  by  directly 
counting  the  a  particles  emitted  by  a  certain  quantity  of  active  sub- 
stance. 

The  first  direct  results  were  yielded  by  the  scintillations  produced  by 
a  particles  on  a  screen  of  zinc  sulfide.  Each  scintillation  being  assumed 
to  be  produced  by  a  single  a  particle,  the  number  of  scintillations  was 

H5 


1399  RADIOACTIVITY. 

determined,  produced  in  a  given  time  by  £.  known  quantity  of  the  active 
substance.  This  gave  the  number  of  a  particles  emitted  by  the  sub- 
stance, and  consequently  the  number  of  atoms  transformed  in  a  given 
time.  Another,  and  very  ingenious,  method  was  first  employed  by 
Rutherford  and  Geiger,  who  utilized  the  ionization  produced  in  a  gas  by  a 
particles.  These  investigators  succeeded  in  determining  the  ionizing 
effect  produced  in  a  rarefied  gas  by  each  a  particle  by  making  use  of  the 
phenomenon  of  ionization  by  shock.  The  entrance  of  each  single  a  par- 
ticle into  the  gas  affects  the  electrometer,  and  all  that  is  necessary  is  to 
count  the  number  of  disturbances  produced  in  a  given  time.  The  two 
methods  have  yielded  well  agreeing  results,  which  indicate  that  radium 
ought  to  be  one-half  destroyed  in  about  2000  years. 

The  destruction  of  radium  is  too  slow  to  be  capable  of  being  detected 
by  direct  experiment.  Nevertheless,  in  order  to  account  for  the  presence 
of  radium  in  minerals,  it  is  necessary  to  assume  that  radium  is  continually 
produced  in  those  minerals,  the  destruction  being  thus  partly  compensa- 
ted for.  The  element  which  appears  evidently  to  be  the  most  capable 
of  changing  into  radium  is  uranium. 

In  fact,  radium  is  always  found  in  uranium  minerals  and,  furthermore, 
uranium  is  radioactive  and  hence  in  a  state  of  decomposition.  Since  the 
radioactivity  of  uranium  is  much  less  intense  than  that  of  radium,  its 
duration  of  life  must  be  much  greater  than  that  of  radium,  and  this  ex- 
plains the  occurrence  of  uranium  in  considerable  quantities  in  nature. 

An  extremely  important  argument  in  support  of  the  accepted  rela- 
tionship between  uranium  and  radium  lies  in  the  constant  ratio  of  the 
quantities  of  the  two  elements  found  in  minerals.  The  constancy  of  this 
ratio,  which  has  been  principally  affirmed  by  the  experiments  of  Bolt- 
wood,  is  readily  explained  if  we  assume  that  radium  is  produced  from 
uranium,  and  that  the  destruction  of  radium  is  much  more  rapid  than  that 
of  uranium.  The  ratio  permits  of  calculating  the  mean  life  of  uranium. 

Attempts  to  demonstrate  directly  the  formation  of  radium  from  ura- 
nium have  shown  that  this  transformation  is  certainly  not  immediate, 
and  that  there  ought  to  exist  at  least  one  substance  intermediate  between 
uranium  and  radium.  This  has  been  confirmed  by  Rutherford  and 
Boltwood's  discovery  of  a  new  substance  capable  of  producing  radium. 
This  new  substance  has  been  named  ionium.  The  mean  life  of  ionium 
being  probably  long,  there  is  hope  that  this  substance  will  be  isolated 
without  much  difficulty. 

The  question  of  the  relationship  between  uranium  and  radium  seemed 
to  be  definitly  settled,  when  recently  Mile.  Gleditsch  announced  that 
the  ratio  of  the  quantities  of  uranium  and  radium  was  not  the  same  in  all 
minerals,  contradicting  the  earlier  results  of  Bolt  wood.  While  the 
ratios  found  by  Mile.  Gleditsch  are  of  the  same  order  of  magnitude, 
they  nevertheless  differ  very  materially  from  one  another.  The  hypothesis 
of  the  formation  of  radium  from  uranium  furnishes  so  simple  an  explana- 
tion of  the  presence  of  radium  in  minerals  that  one  can  hardly  abandon 
it.  As  a  matter  of  fact,  however,  the  conditions  of  formation  of  radium 
appear  to  be  complex  and  not  yet  completely  elucidated.  Unquestion- 
ably, further  study  of  the  relative  quantities  of  the  different  active  sub- 
stances in  minerals  will  yield  new  and  important  results.  Such  study 
will  also  be  of  great  usefulness  in  geology. 

146 


GENERAL,    PHYSICAL   AND    INORGANIC.  1400 

If  the  phenomena  of  radioactivity  indicate  atomic  transformation,  one 
expects  to  find  radioactive  energy,  corresponding  to  the  transformation 
of  atoms,  to  be  far  greater  than  the  energy  changes  generally  accompany- 
ing the  transformation  of  molecules.  That  this  is  true  is  shown  by  Pierre 
Curie  and  Laborde's  discovery  of  the  enormous  quantity  of  energy  given 
off  by  radium.  One  gram  of  radium  in  radioactive  equilibrium  would 
produce  about  1 20  calories  of  heat  in  an  hour.  The  quantity  of  heat  that 
would  be  set  free  by  the  complete  transformation  of  one  gram  of  radium 
is  nearly  the  same  as  that  produced  by  the  combustion  of  a  ton  of  coal. 
Most  of  this  heat  has  been  shown  to  come  from  the  kinetic  energy  of  the 
a  particles.  Heat  has  also  been  shown  to  be  developed  by  actinium, 
thorium,  and  polonium.  Radioactivity  thus  constitutes  an  extremely 
important  source  of  energy.  A  very  slight  proportion  of  radium  in  the 
sun  (about  i  gram  per  cubic  meter)  would  be  sufficient  to  account  for 
all  the  energy  radiated  by  it.  The  energy  radiated  by  our  own  planet 
seems  to  be  more  than  compensated  for  by  the  radium  contained  in  its 
crust,  so  that  the  progressive  cooling  of  the  earth,  once  generally  accepted, 
now  seems  to  be  problematic.  It  seems  legitimate  to  assume  that  radio- 
activity constitutes  one  of  the  principal  sources  of  the  energy  radiated 
in  the  universe.  No  other  hypothesis  is  based  on  an  equally  serious  ex- 
perimental foundation. 

The  atomic  transformation  of  radioactivity  takes  place  under  very  pecul- 
iar conditions.  As  already  stated,  the  phenomenon  is  spontaneous, 
apparently  causeless.  Moreover,  no  method  is  as  yet  known  by  which 
such  transformations  might  be  brought  about  or  stopped,  or  even  in  the 
least  degree  hastened  or  slowed  up.  Elevation  of  temperature,  which  is 
so  sure  to  increase  the  velocity  of  chemical  reactions,  seems  to  have  no 
effect  whatever  on  radioactive  transformations.  Thus,  the  characteris- 
tic constant  of  the  destruction  of  radium  emanation  is  the  same  at  high 
temperatures  as  at  the  temperature  of  liquid  air.  Neither  does  the 
nature  of  an  inactive  chemical  element  combined  with  the  radioactive 
atom  seem  to  have  any  influence  upon  the  velocity  of  its  destruction. 
As  yet,  we  are  mere  spectators,  observing  the  transformation  of  atoms, 
but  unable  to  interfere  with  it  in  any  way. 

The  transformation  follows  a  probability  law  identical  with  the  law  of 
mass  action  followed  by  chemical  reactions:  the  number  of  atoms  trans- 
formed per  unit  of  time  is  at  any  instant  proportional  to  the  total  number 
of  atoms  present.  No  simple  and  satisfactory  hypothesis,  however,  has 
been  advanced  explaining  this  fact.  In  the  case  of  mono-molecular 
chemical  reactions,  the  fact  that  the  transformation  takes  place  grad- 
ually is  explained  on  the  assumption  that  all  the  molecules  present  are 
not  in  the  same  condition,  either  owing  to  collisions  between  the  mole- 
cules or  because  of  differences  in  whatever  motion  may  be  going  on  within 
the  molecules  themselves.  The  transformation  of  a  given  molecule  is 
instantaneous,  but  the  molecule  will  not  undergo  transformation  unless 
it  happens  to  get  into  a  certain  condition  necessary  for  it.  The  proba- 
bility law  must  then  remain  the  same  as  long  as  the  number  of  molecules 
remains  very  great  and  the  external  conditions  of  the  reaction  remain 
the  same.  In  the  case  of  radioactive  transformations,  external  condi- 
tions (e.  g.,  of  temperature)  and  intermolecular  collisions  ought  to  have 
no  effect.  Therefore,  only  the  motion  within  the  interior  of  the  atom 

147 


1401  RADIOACTIVITY. 

can  be  invoked  in  an  effort  to  explain  why,  in  one  and  the  same  substance, 
some  atoms  break  down  immediately  after  being  formed,  while  others 
are  destined  to  live  hundreds  or  even  thousands  of  years  before  under- 
going transformation. 

It  is  imaginable  that  there  exists  in  space  a  special  field  of  force  which 
influences  intra-atomic  motion  and  is  therefore  capable  of  causing  the 
disintegration  of  atoms.  The  action  of  such  a  force  must  then  be  inde- 
pendent of  any  translatory  motion  of  the  atoms.  There  is,  however,  at 
present  absolutely  no  indication  of  the  existence  of  such  a  force  in  space. 

If  the  transformation  is  not  brought  about  by  an  external  force,  and  if 
external  conditions  of  pressure,  temperature,  etc.,  have  really  no  influ- 
ence upon  the  progress  of  radioactive  changes,  one  is  led  to  assume 
that  the  destiny  of  a  given  atom  is  completely  determined  at  the  very 
moment  of  its  formation,  that  at  that  moment  it  is  already  in  such  a  state 
that  its  transformation  must  take  place  after  exactly  a  certain  interval 
of  time.  In  that  case  a  radioactive  element  must  be  considered  as 
made  up  of  atoms  of  different  nature,  some  destined  to  very  speedy  de- 
struction, others  to  a  more  or  less  prolonged  existence.  It  is  not  un- 
thinkable that  these  different  atoms  of  one  and  the  same  radioactive  ele- 
ment may  some  day  be  separated. 

In  order  to  account  for  the  exponential  law  of  spontaneous  destruction, 
it  is  necessary,  in  that  case,  to  assume  that  the  distribution  of  life  dura- 
tions among  the  atoms  at  the  moment  of  their  formation  is  represented 
by  a  simple  exponential  function,  the  atoms  of  short  life  being  much  more 
numerous  than  those  of  long  life.  It  is,  however,  difficult  to  imagine 
what  can  possibly  be  the  cause  of  such  a  law  of  distribution,  and  con- 
siderations like  the  above  only  show  that  while  the  laws  of  radioactive 
transformations  have  been  determined  with  precision  and  are  well 
known,  the  initial  cause  of  the  phenomena  is  as  yet  altogether  obscure. 

In  concluding  this  summary,  I  will  mention  the  attempts  that  have 
been  made  with  a  view  to  artificially  bringing  about  atomic  transforma- 
tions with  the  aid  of  radioactive  energy.  Some  results  in  this  connec- 
tion have  been  published  by  Ramsay  and  Cameron.  They  believed 
that  by  the  action  of  radium  emanation  upon  water  they  had  succeeded 
in  producing  neon.  They  further  believed  that  by  the  action  of  the 
emanation  upon  a  salt  of  copper  they  had  produced  alkali  metals:  the 
formation  of  lithium  appeared  to  have  been  especially  well  demonstrated. 

These  results  have,  unfortunately,  been  shown  to  be  erroneous.  Mme. 
Curie  and  Mile.  Gleditsch  repeated  the  experiments  on  the  formation  of 
lithium  and  found  that  when  no  other  than  platinum  vessels  were  used, 
the  appearance  of  lithium  could  not  be  detected ;  in  Ramsay  and  Cameron's 
experiments  the  lithium  came  from  the  glass  of  the  apparatus  employed. 
Similarly,  Rutherford  and  Royds  have  re-investigated  the  effect  of  emana- 
tion upon  water  and  have  failed  to  obtain  any  neon.  I,  too,  have  failed 
to  find  neon  in  the  gases  evolved  by  a  solution  of  radium.  The  neon 
found  by  Ramsay  and  Cameron  must  have  come  from  a  small  quantity 
of  air  introduced  by  accident. 

So  it  may  be  said  that  up  to  the  present  time  no  atomic  transmutation 
has  been  produced  artificially.  All  we  can  do  is  to  subject  to  inquiry 
spontaneous  transmutations  which  we  cannot  control.  A  long  step, 

148 


GENERAL,    PHYSICAL   AND   INORGANIC.  1402 

therefore,    remains   to   be   taken   before   the   dream   of  the  alchemists 
has  been  realized.1 

CLARK  UNIVERSITY.  WORCESTER.  MASS. 

1  New  results  have  been  published  by  Ramsay  and  Gray.  According  to  these 
investigators,  carbon  dioxide  may  be  produced  by  the  action  of  radium  emanation 
upon  compounds  of  thorium,  zirconium,  silicon,  etc.  But  inasmuch  as  carbon  com- 
pounds may  easily  find  their  way  into  apparatus  by  accident,  it  is  difficult  to  establish 
beyond  doubt  a  transformation  of  the  elements  thorium  or  zirconium  into  carbon. 
The  authors  themselves  admit  that  their  experiments  are  not  conclusive. 


149 


Duplicate 
Stanford  Lib. 


